Yeah, you knew this would happen eventually. Not posting to any comms since both sides will attack me, but I'm sorely tempted to make some macros from this.
So after some discussion, I've got the following list:
Doctor Manhattan: Would have to be C.C. since she's the only one in Geass with the same blank outlook on everything. (Season one C.C. though - R2 C.C. actually started having emotions towards normal things so it wouldn't really work.
Veidt: ...Schneizel? *dives for cover* Well, they did have the same "solution" to everything. Except Veidt didn't have Geass to get in the way.
Silk Spectre II: Luluko FTW
Nite Owl II: In keeping with the Luluko thing it kinda has to be either Kallen or Shirley - I'm leaning towards Kallen since she's the one that can actually hurt things/people, but then again her personality isn't quite right.
Rorshach: Maybe Rolo? I don't really think anyone in Geass works for this one.
The Comedian: no idea. It depends on the least dodgy person, and on who Schneizel can throw out a window. XD
As for minor characters...
Kanon is definitely either Veidt's secretary or Bubastis. *snerk*
The others...I really don't know?