GURPS combat is complex (second only to Hero, IMHO) and would be utterly useless for long-distance play-by-text gaming.

A modified form of Amber diceless, or Everway, might be good, if a system were needed. I'm... a bit nervous about going systemless. I'd love to modify Houses of the Blooded for it, but I think even minimal dice-rolling would kill an online post-based instead of chatroom-based game.

I've never quite been able to figure out the interactive-story RPG thing. Willing to try, for a world I love as much as the Vorkosiverse, but still nervous.

What systems does your group like for one-shots?