If Diocletian and Maximian could be persuaded to accept Carausius as co-emperor, that would be a Britannian part of the empire in the late 280s AD.
I'm still not following how that's germane to what I'm saying. The Roman Empire was focused on Mediterranean sealanes. Trade with the east, while important economically, isn't really relevant to the question of how large the Roman Empire could become.
It is not going to make much impact; the Romans had already outflanked Persia by sailing from Egypt to India. Increasing voyages to the Indus river region would serve equally as well and be more cost effective.So, if the Romans conquered Persia or even only Mesopotamia, they would have been able to bypass intermediaries, to reduce the economic impact of outflow of metals and capital and to equate their foreign trade balance.
What would be required is capital investment. If a senator can make a bigger fortune in the spice trade than tax farming, others will follow suit. The thing is that none of them did so. They left trade in the hands of natives.
It is not going to make much impact; the Romans had already outflanked Persia by sailing from Egypt to India. Increasing voyages to the Indus river region would serve equally as well and be more cost effective.
On equalising trade balance, occupation of the Middle East is not the way forward. Sailing to India, the Spice Islands and China are the only realistic options. The Romans had ports in the Red Sea, which are nearer to the spice and silk sources than the early Modern Europeans.
Who said that a senator has to enter Egypt? He can send agents/clients1) Entering Egypt as a senator was forbidden, so investing there was difficult for the highest order.
No evidence of a pirate threat, at least one that the early modern Europeans faced. If one develops then military action can then be taken.However, it is shorter to sail from Mesopotamia (Charax) to India than to have to circumnavigate all of Arabia when starting in Egypt. Also, the Parthians/Persians controlled the land route that never disappeared completly.
But why didn't they sailed more often than they did OTL? I doubt the Parthians had an effective fleet to fight against the pirates endangering the eastern see routes, so the Romans need to deploy one in the Indian ocean (and not only in the Red Sea as OTL). Such a fleet would need bases in Arabia and maybe also on the Persian coast, so we return to the point of departure.
No evidence of a pirate threat, at least one that the early modern Europeans faced.
At the present day voyages are made to India every year: and companies of archers are carried on board the vessels, as those seas are greatly infested with pirates.
If one develops then military action can then be taken.
As for why they did not sail is because they did not have companies as the early modern Europeans did. If you are the owner of a ship and it sinks you go out of business. If you have shares in eight ships and one sinks then you are still in business if the loss of one is more than covered from the profits from the other seven.
In terms of economics, a mercantile fleet sails between Egypt and India requires less capital and maintenance than land caravans crossing the Middle East plus the legions required control the roads.
No reason why they can not. After all in the medieval era associations were formed and dissolved. It just takes one group to make the leap forward and not dissolve at the end of a voyage. In fact the Romans may have already done so albeit at an informal level. Not necessarily something that a historian would think of recording.IIRC, Roman merchants knew the concept of joining their capital to fund mercantile expeditions, but these associations dissolved after the voyage and didn't evolve into joint-stock companes. How can we make them form real, permanent companies?
No reason why they can not. After all in the medieval era associations were formed and dissolved. It just takes one group to make the leap forward and not dissolve at the end of a voyage. In fact the Romans may have already done so albeit at an informal level. Not necessarily something that a historian would think of recording.
Why not? It appears that he was based on two separate and very real men, so there was a void to be filled...So King Arthur?