i have D&D 3.5, warhammer fantasy role play, feng shui, slayers d20 and besm.
im working on a rule set for pure forum play, if you have any ideas of how it should be done id love to hear them.
i dont think it should be to hard to run it completly over the gaia forums since it does have a dice action. the problem comes in with posting. The DM makeing time limits for actions in an open scenario (towns and such) would be a remedy for that. The DM would post a description of the scene then the players would be able to react within the time limit, say a 10 count, were the DM will post in replies a countdown while the players post their actions. for active scenes like a battle a shorter time limit since its generaly attack in a fashion or movement. so it would go DM designates whos turn it is, they post their reaction, DM states what needs to be rolled, player roles. For spacific details that only need to go to one player the IM system will be great.
aside from forum play im going to set up a team speak server, gaia will still be used for dice roling, or try using a program ive found that allows for play over the net, it has a dice roller and graphic interface.
http://glittercomm.com/