Well, we actually have JRPG characters in Smash in the form of Pokémon and Fire Emblem characters. Of course, FE is more of a SRPG and Shulk looks more like traditional JRPG protagonists, so I understand your point.
Isaac would be interesting too, even though I never played Golden Sun before, but I think Robin and Shulk already stole his thunder. FE:A and Xenoblade characters are more familiar to most players these days than Isaac is.
No doubt. Smash is a once in a while chance and not everyone has the chance to be in.
And now for some theory crafting: should the leak be entirely true, I think Dark Pit was included because Sakurai wanted to add a character he created to this Smash game. Pit and Palutena aren't Sakurai's creations, having debuted in the first Kid Icarus game, but Dark Pit is since he was created for Uprising...
Not true!
Europe gets the game in October 3rd, just like America. Germany is the exception, getting the game on retailers one day earlier since October 3rd is a holiday there.