I've been thinking about possible Sicily/Genoa interactions by way of event, Archduke, and I've come up with the following:
1) Early in the game, I think Genoa should support Sicilian claims on the Marches (Marche province) if Sicily chose to compromise with the Republic in event 201701.
2) The Genoese would probably also support a Sicilian bid for Romanga over the Papal and Milanese claims. The conflict over Romanga is something that I've yet to write, it will probably happen around 1440 and will start with the Papal States.
3) The Genoa/Sicily conflict begins around 1590. I think it could be useful to have an "End of the Conflict" event around 1630. If both are still alive and neither one is a vassal of the other, the war is a stalemate. At this point, we could have them swap some provinces back, if they were taken, (Corsica, Liguria, Venice and Istria to Genoa; Sicily, Messina, Apulia and Naples to Two Sicilies), alter core provinces and then have some nice events for the two of them cooperating later.
4) I also think that it would be nice to have an event if Genoa wins the war and also one if Sicily wins the war. What constitutes "winning" is subject to debate, but I have some idea about what the potential rewards could be.
Ultimately, I would like to revisit my own minor Genoa/Sicily events in the major_gen.txt file, just to make it all sync up with whatever uniform scheme we come up with.
Cheers.