Have everybody make a map and then see if you can't put all the entries into one Megawad
Lol.
To be fair you can put just as much maps as you can now, I belive, there's a twist however.
This only works with zdoom-based or "extended (functions and limits wise) ports, so it will not work in Chocolate, Crispy, Retro, But definitely will work in, say, gz, k8vavoom, edge (preferable to use edge-classic since original port's tranny dev made it unstable as fuck and guys behind e-c make their best to somewhat fix it)
I mean, look into DUMB3 that was hosted by Terminus and how much of maps were contributed there.
edit: Ah yeah I forgot about DSDA port... duh, shame on me.
I think the concept of KF having its own doom mapping project sounds cool, and I support it being ZDoom based as ArticleWriter said. If anything ever comes of it I'd map for it.
I'd advice to make it Boom\MBF-based however, so people will have some better understatement toward mapping basis.
Nah sure, you can start from UDMF (like me and a fucklot of people ever done at first because the amount of "cool stuff"), but... eh, better to stick to more classic approach, for your first endeavors.
if you want something zdoom-esque you'd need to make an entire Total Conversion. Again, I can help with graphics and palette for it, to certain point, but you need to understand that this approach might to take years and many of people involved will lose their interest in the process. More than just a few mappers, mind you.