It's probably not quite as serious as the other suggestions/options in the thread, but I'd love to see/participate in a new roleplay-style thread in the vein of 'This is the Liber Astartes', especially now that we have Xenos in the mix! Backreading, it seemed like a phenomenal idea to develop the participants' original characters, Their Dudes, and life aboard the Legio Fortress.
...I had so many plans for this year, brothers.
Foremost amongst them was a play-by-post, turn-based game (like the kraken hunts from long ago on the Space Wolf forum, but I can't seem to find the old threads ) featuring us Liberites as our in-universe Legio-member selves. We'd wind up on a mission to a jungle world, that quickly goes terribly, terribly awry, becoming an all-out fight for survival against some hyper-deadly wildlife, punctuated by everyone's descriptions of the battle/inner monologues/audibly blaming Ace for everything going wrong.
I was even going to award each Liberite re-rolls for saves/hits/etc for taking part in general Liber activity, either writing up your own Chapter/Warband/Forgeworld/Waaagh/etc or commenting on the efforts of others.
But this year has been a constant onslaught of stuff to do in real life, so my plans have stalled out completely.
More on topic, I'd be fine with either putting together a new setting or going back to the Liber Cluster; so long as I'm not required to take charge of it in either case.