Ah well, I haven't done much but make a few posts and then be negligent myself about reccing! :) A fake-trailers theme sounds awesome! You can basically just announce that it as a theme exists, and how long it'll run for (or I can, if you'd rather! And I'll keep an eye out for necessary tagging) If there's anything additional you want to do as part of the theme, during or after, have at it!

And festivids recs is probably a workable thing too. I don't think the festivids comm itself does anything like that? Though they may put up a post for people to link their recs lists, which I think a lot of people do put together? But this is the first year I've properly done it, so I'm not sure how it all happens.