Venice would be a great addition to the aoe series, but it would fit inside the aoe2 or aoe4 timeframe.
In the aoe3 timeframe, Venice was an indipendent and diplomatic important states for some time, but not enough to justify making it into a civ. I would much rather see an Italian civ with the US state sistem which also includes Venice instead.
If you are interested though, I’ve made several Civ design for aoe2 and aoe4 of Venice, feel free to check it out (although the aoe4 design is outdated and will soon receive a massive change).
Actually, Venice still had an important fleet even at the moment of his downfall at the hands of napoleon, although it was mostly dedicated to protect merchant convoys.