I wouldn't call it a bad idea - it certainly would be a neat addiition to Civ4, but I'm not sure how it would fit into Civ5. Not that I'm defending embarkation (I could do with or without it). It seems that the unit would require changing (or eliminating, if that's what your suggesting) embarkation mechanics, which is probably doable; I dunno, I'm not a modder. However, it also would seem necessary to restructure how resources work in the game, and I doubt that's easy. Plus, it seems like your making a unit that serves as a military unit, a civilian/merchant/trade unit, and a transport unit all in one - not that you couldn't make a unit that serves these roles and have it be somewhat balanced, just that the function seems unclear. Your ideas, if I'm understanding them correctly, seem like they'd be more well suited as a mod that consists of several units, instead of adding just one unit.Galleons could become Long Distance Cargo Vessels. What I mean by this is that in order to bring in resources from cities not on your original continent/island you would need a Galleon (and later on, when Galleons become obsolete, other means of transportation)
To transport colonists and military units to far away (colonial) lands you need Galleons.
Galleons do not sink in Ocean tiles(hexes) unlike their predecessor transport ships, are armed with cannons and capable of, if not sinking, then at least seriously damaging any frigates attempting to sink them or board them (in order to steal some of Galleon's cargo and convert it to gold for their civ)
Bad idea?
PS. Please stop insisting that this whole 'Embarkation" idea introduced in CI V is a good one, when it really isn't.
Maybe you could elaborate more?