Yup. But I guess first they actually need to be sure who is starting Games 1 and 2 (i.e. they aren't needed in Houston.
I reckon you also don't even decide until after Game 1 is played. If you win it, then at that point you designate one guy as your NLDS Game 1 starter who is not available unless absolutely necessary, and then draw up the Game 3 plan accordingly. If you lose it then everyone's available (for Game 2 as well). Either way, nobody is a perfect, worry-free #3 or #4.
No matter how it goes you are going to have four former starters in a different role (or off the roster) in that first round and even if they just decide Suarez is a reliever I doubt he's available for two games.
Hey, fun to even think about (if premature).
On another note - do the Phillies quietly obtain the waiver and announce Thomson's permanent status heading out of the final weekend (or perhaps sooner, if the race is tight) for a little boost?