At the start of the thread, Massalia and Rome were allies. with the League sending aid to Roman conflicts in Italy. Soon after I noticed that the League was increasingly abstaining from what may not have technically been obligations to aid Rome, but which I bet many Romans felt they should have helped with. Now, we see the League helping cities of Magna Graecia evacuate their peoples and resettle them in their territory, leaving empty shells for the Romans to rule over. Insofar as the Romans are thus saved casualties and offered tracts of land they can re-colonize with their own chosen subjects, the League might represent this as a favor, but the premise of friendship between Massalia and Rome is getting thinner and thinner.
We have yet, however, to witness the League turning decisively and directly against the Romans; so far it has been a matter of drifting away and evasion of conflict.
It is not clear to me whether the POD in the near future the author has spoken of has come or gone or not, but it does seem clear that long ago, probably before this thread got past the first page, the TL has already diverged from OTL. OTL I don't believe the League ever reorganized itself on such strongly democratic lines, much less taken the recent reform of a centralized federal republic. And OTL, I believe the Massaliotes kept in diplomatic lockstep with the Romans, never doing anything to offend the Republic and always at the ready to aid them. Their reward for this, in the longer run, was to have Rome systemically strip the city itself of its former dependencies and make these directly Roman. The city continued to prosper and was not directly conquered--until late in the Republic's civil-war-torn years, when they supported the Republic against Julius Caesar who was in opposition to the established set of rulers at the moment.
Here for good or ill, the League has taken a more active role, and works methodically toward its own interest. Will this necessarily mean conflict with Rome? Certainly as things stand, Rome's avenue toward glory in the northwest is blocked by the League. The League also stands between Italy and Iberia, though a sea connection would not be impossible--but not playing to Roman strength, which is that of armies on land, not sea power. One can imagine a scenario where a Roman/Massaliot alliance attacks Carthaginian Iberia, but in the ATL development of the League we have already seen, the Greek federation will not be content to simply let the Romans take the territory they might thus free. If it is the other way round, the League facing a devastating invasion from Carthage's Iberian holdings and calling on the Romans to assist their defense (obviously in Rome's interest to do so, with the ML interposed as a buffer state) perhaps then the Massaliot government might sign off on Roman colonies in Iberia as the price of Roman aid.
The League clearly has even more ambitions than the domination and absorption of Gaul, all of which would bring her into conflict with Roman ambitions if we assume the Romans are not diverted from their OTL course. I'm pretty sure that they haven't moved on eastern Iberia because Carthage does hold it strongly--for the moment. It is this grip on the eastern half of the peninsula that allows Carthage to monopolize the Atlantic trade--or did until the recent annexation of a salient into Aquitani and the new port on the Bay of Biscay (or whatever the Greco-Classical name they would give it, beyond Ocean-Atlantic, would be). The ambition to break Carthaginian power is something the League is coming to share with the Romans, and may be the basis of their historic and OTL eternal alliance holding somewhat longer. But I feel that already serious fault lines are forming. League leadership may postpone any direct confrontation with Rome for quite a while yet, but the price of their doing so is allowing the Romans to consolidate control over increasing area. With the conquest of the southernmost reaches of Italy, the Romans have accomplished something already worth more than just so many thousands of square kilometers added to their domain; they have eliminated a potential front on which they can be attacked. Not entirely obviously; landings by invasion fleets are a thing in this era, and Carthage still controls Sicily, which is very near. If the Romans get the upper hand in Sicily as well, then they have in effect got control over all Italy, and can concentrate more defensive or offensive force in the North. With the Alps being largely a barrier, this means they can focus either northeast, or northwest--to move into the Balkan peninsula toward Greece, or to move into Gaul. OTL when the Romans moved northwest, Massaliot power was so diffuse that either that city did not perceive the Roman advance as a threat at all, or if they did, they were too weak to oppose it and made the best of it by obsequious friendship with the rising superpower. Here it is already too late for that; Roman ambitions against Gaul mean ambitions against Massalia, whereas the Massaliotes seem to have expanded and developed their armies enough to give the Roman Legions a serious challenge. At the same time, by taking more direct and deeper control of the neighboring Gaulish peoples, they deprive the Romans of the pretexts and perhaps motivations they had to move in that direction at all.
Therefore the Romans may not even wish to proceed northwest, and let the border of Cisalpine Gaul rest peacefully. That would tend then divert their ambitions eastward, but the Balkans are tough sledding; OTL the Empire never made much of the interior, with the relevance of Illyria being mainly its strip of coastland, aka "Dalmatia." Dalmatia in turn leads to Epiros, which is Pyrrhus's home and thus defended by himself and all the resources of Macedon and northern Greece he currently holds. And at this moment, he is an ally of Massalia!
This alliance may break up when Pyrrhus dies. But even without the super-general of the age blocking the route, the Adriatic shore is not all that attractive. It would perhaps be conceivable the Romans get diverted northeast indeed, through OTL Serbia to the passes leading into the great valley of Pannonia, but OTL the Romans never did much with this route and that resource despite having the whole Mediterranean-spanning empire to draw on, so presumably that is no royal road to wealth and power either in this age.
If the Romans consider themselves boxed in on land, they might still take to the sea and range around trying to round out their holdings. I have suggested they share the ambition the Massaloits have to eliminate Carthage as a rival, one that has already moved to box in the rising powers, but the difference is that the Massaloites have developed an alternative path to the Med. The Romans have nothing in that respect unless they can dislodge Carthage from Iberia. A naval conflict might be nextt, one where unlike OTL an alt-Hannibal does not have the option of invading Roman land overland at all...
...unless Massalia allies with Carthage!
If we figure Massalia instinctively dreads the day they must face the Romans at last and postpones it as long as possible, they have to leave Rome free to try and secure Sicily for itself, while not amassing threatening force on the boundaries of Cisalpine Gaul. If they do that, Rome might also be able to seize Corsica and Sardinia, and then the eastern end including Massalia itself is threatened pretty direly.
It is hard to see any of the three powers of Massalia, Rome or Carthage forming a lasting alliance. Actually a Massalian/Roman alliance would have some merit--OTL this was done and resulted in the gradual annexation of the former to the latter. The more aggressive League here seems unlikely to roll over to that degree, but visionary statesmen might foresee an indefinite partition of interests, with Rome focused eastward to secure Hellas and the rich lands of the eastern Med while Massalia bypasses, undercuts, and ultimately absorbs Carthaginian western holdings.
But the author has already leapfrogged past this, with the Massaliotes seeking formal alliance with Pyrrhus and Ptolemy. Indeed, why should such Hellenes as the Massaliotes consign the vast holdings of the Hellenistic heirs to Alexander to a bunch of Latin barbarians?
OTL the path Rome took to invincible power over the east was to first secure a rustic western hinterland, absorbing both the Massaliote and Carthaginian spheres completely, before being drawn into the squabbles of the Hellenes to the east. If Rome does not do this but is diverted eastward directly, it seems doubtful they'd have the power to accomplish what they did OTL, even given extra centuries in which to try.
An alliance between Carthage and Massalia would be unstable and opportunistic, necessarily focused on knocking Rome out as a mutual threat. Once this is accomplished, if it can be, the two are basically contending to control the same territory and must come to blows; meanwhile neither can be focused on securing the eastern end of the trade pipeline that was the ultimate prize Rome won OTL. The author seems to have leapt ahead to Massaliote victory in awarding that League the alliance with Pyrrhus and Ptolemy--again of the three western powers, only one is ruled by Hellenes. But for Massalia to trade with the Atlantic goods she has gotten her hands on to the rich markets of the east, her ships must run a gauntlet contested between Rome and Carthage!
Might a Roman-Punic alliance to crush Massalia be in the cards then? If Rome absorbs the nearby city-state as a conquered province, would the Carthaginians see Rome as any less of a rival than Massalia had been? Perhaps, if the Romans will partition the Iberian holdings, Tolosa, and Aquitani to Carthage, and content herself with eastern Massaliote lands and the route up Saone-Rhone which reaches to inland Europe the Carthaginians had no relations with anyway, the Romans may then be rich enough to write off southwestern Gaul, Iberia, all of North Africa west of Libya, and focus as OTL on the endgame in the eastern Med.
But again, while suitably enlightened and foresightful leaders in Carthage and Rome might conceivably share such a vision, the more obvious course to take is for one to eliminate the other and take over its holdings and then turn eastward.
The triple standoff is interesting, I won't dare predict how the author intends to resolve!
What is quite clear is, whatever the "POD" was, it is well in the past by now.
