That's fine. (And I didn't actually do the math, anyway.) It's still a lot of extra effort and the rest of the team will take a lot of convincing to get them do to so much extra work.
I definitely see your point there, it might not be an easy sell.
Well, that would be assuming they're intimidated by the game's difficulty (a lot of players aren't) any they like all your characters (which is highly unlikely) enough to keep them around. Not only that, that'd be assuming they like the mechanics attached to each of them. There are some players, for instance, who HATE stealth-based gameplay. (Bunch of gung ho morons, if you ask me.) They'd kill off a stealth-based character on principle just to avoid sections designed for stealth, even if they like that character.
The way I see it, is that rushing in and deliberately throwing lives away will be severely punished, both on a gameplay as an ethical level. I don't intend to go lightly over a character dying.
If that doesn't stop them from playing a bit more conservative and they end up losing all of their characters and then complain about the game being stupid, I guess the game wasn't for them. I was always okay with it being a rather polarizing game.
I actually think people throwing a character away because they don't like the playstyle they offer is interesting, as I will rub in how heartless their decision was. Also, they will still encounter puzzles that highly benefit from stealth, just a tad less and less essential puzzles will still require stealth.