This is the kind of thing I was looking for. I knew there'd been talk of the Venetians revamping the old Nile-Red Sea Canal, which would give them a massive leg up in the Oriental trade, and also encourage them to develop the kind of Atlantic-type vessels needed to maintain a strong presence outside the Med. Sea. I like the POD. Temporary anti-wank followed by increased focus on the real revenue stream...
Unfortunately IOTL Venice developed the galleass (which performed very well at Lepanto as a gunnery platform, but was handicapped by its own weight, and had to be towed by normal galleys) rather than follow the Portuguese example (nao). The choice of having galleons was made just in the 1630s, too late for entering the India game (and in any case an independent Egypt disappeared in 1515 - no more chances of a very early canal, unless there is a very different relation with the Ottomans). It would be interesting to see what Venice plus Egypt might do: assume the Visconti state survives (which does not necessarily means a big Milan wank: say Gian Galeazzo lives another 15 years, and can consolidate his domains as well as groom his sons before dieing), so that Venice is not suckered into a terrafirma expansion. In TTL Venice stay concentrated on the east, even if it does not change too much the outcome of the war with the Ottomans (maybe they end up holding a few more fortresses in Morea, I don't think that Negroponte can be saved, much less Thessalonika, which is the first to go). However when Constantinople falls, Venice starts more in earnest to look for alternative routes to the east: contacts with the Safavids for sure, but the largest investment is made in opening up friendly relations with Egypt, and having a go at the restoration of the Ptolemaic channel. Vasco de Gama arrives in India circumnavigating Africa in the last years of the 15th century: if the Egyptian shift happens by 1460 (in the wake of the fall of Constantinople), by 1480-1485 the canal might have been re-opened and the first Venetian ships (galleys) should be docking in India in the early 1480s. It will not take much to realise that a sailing ship (caravel, in these years) is a better proposition, nor it would be difficult to procure some ships from Portugal or Spain. The carrack also (nao) should be almost developed, even if not completely and I believe it will be next step. More loading capacity, better speed, better gunnery platform. When Vasco de Gama reaches India he will find the Venetians already in place.
Sooner or later the Ottomans will come sniffing at Egypt, maybe even earlier than OTL if the canal is such a commercial bonanza. IOTL the Mameluks did not put up a big show; ITTL Egypt will be richer, and much more open to European influences (better artillery). There will be a strong allied fleet covering the coast of Outremer, with Cyprus as its lynchpin. The roads to reach Egypt from Anatolia are not too many, and most of the time they follow the coast. It might end up in a very different way.