Independent ancient Spain

Reading Appian’s Iberike lately, with his accounts of the Numantine war and Viriathus’ war, I was impressed with the ferocity and determination of Spanish resistance to Rome, and I was wondering what it would take to produce a unified, independent, Spain under native rule (so no Barcid or Sertorian régimes need apply) by, say, 50 BC.

Clearly some of the coastal Iberian cities, like Saguntum, were fully-developed Mediterranean city-states, literate in their own language; there was considerable wealth available, as the loot taken by successive Roman armies testifies; and the Spanish, whether Iberian, Celtiberian or Lusitanian, were tough and versatile soldiers, in great demand as mercenaries in foreign armies, and often prepared to resist conquest to the point of mass suicide rather than surrender.

So how and when could Spain, or even a substantial part of it, have been unified under local, rather than Punic or Roman, rule?
Triple stability.

A Carthaginian and Greek alliance against Rome. Egypt was also powerfull but didn't have timber resources for a navy, and didn't have constant fighting against neighbors to keep it's army in good shape.
Later the French area would also have unified under pressure from a weaker but still powerfull Rome. Perhaps Northern Italy would have dominated the Italian peninsula. Another empire in the Panonian basin? Independent Sardinia, Corsica, and Sicily?
I would have prefered a multipolar Mediterranean. More interesting and probably more progressive.
Tartessos disappears when, before 450 BC? Certainly quite early. Not sure how much is known about it these days. A surviving Tartessos as a basis for unifying Spain is a possibility, yes.

Don't see how a Greek-Carthaginian resistance to Rome is going to lead to an independent unified Spain - more likely to a Carthaginian-ruled Spain, which we nearly got anyway.
A long time ago, I started a timeline where Rome never became a major power. By around 200 BC, Carthage dominated the southern part of Spain, and there was no rival power to drive them out. In my timeline, though, Carthage got involved in a series of wars against a coalition of Greek city-states in Sicily and southern Italy, who ended up being supported by a loosely organized Celtic-Etruscan Kingdom that ruled part of Italy.

If Carthage was eventually defeated, a native power might arise that would unify Spain under native rule.