What were the odds of a Mediterranean-girdling empire, especially one that has not just coastal enclaves, but a contiguous land presence around most of the sea, in the event Rome does not rise into that position?
What other polities might be best-positioned to do that?
Another Italian city state we hardly think of, or a Kingdom like the Etruscans?
the Carthaginians?
A Macedonian or Diadochi based empire?
An enduring Persian empire
a Gallic empire
a Berber or Mauretanian empire
a Greek-speaking polis in Greece, Sicily or the west med pulls a Rome?
an empire based on some now obscure ethnic group like Thracians, Illyrians, Dacians, Phrygians or other Anatolian peoples?
An Iberian empire
A Germanic, Scythian, Slavic or Sarmatian empire
If we wanted a polity based on a major European island like Cyprus, Rhodes, Crete, Sicily, Sardinia, Corsica, Majorca or Crimea have a decent shot at forming a Mediterranean-wide thalassocracy or coastal empire or more, which island would be the most plausible point of origin for it?