I actually cried at the end of Grim Fandango. Well not really because my brother was watching the cutscene over my shoulder, but I didn't talk much and cried later if memory serves.
(Bye Bye Dignity!)
Anyway, I think the boat idea is pretty good, except that it'd be hard to rebuild a boat whilst sailing. And being confined to a boat would frustrate me.
I think a direct sequel would cheapen anything and everything Manny did in Grim Fandango, and Glottis...as much as I love the guy, I dont think he could be a main character in an adventure game.
People who call me 'paranoid' are probably in on the plot.