I'd be up for this... but not as a DM mostly because lately that's all I seem to be doing ...
I think the best way would probably be a combined play-by-post, and "Living Setting" setup... but remove the specific ruleset function from the "living setting" bit... This would allow people who worry about speed to simply arrange a VTT session and get things done... and people who can't keep some kind of VTT schedule to continue to contribute...