Hmmm, I would say try to plan stuff out as much as possible and I'll take hiatuses into consideration. If you plan on hiatusing, I would just make a note of that and post it with your tally thread comment. If a lot of character absences seem to be a problem for one team or another or multiple teams, I'll try to figure out a way to weight things so it's fair. But as of right now, I don't think one or two hiatuses will effect people much since I'm sure there will be a decent amount of people uninterested/slow/etc.

TL;DR just do as much as you can and/or want to and I'll see how things work out!