Originally Posted by Geoffrey S
Why not work on what you've already got in that list? It's already a massive amount of work you've set yourself up for, if nothing else I'd suggest working on an initial version with an absolute minimum of (new) factions just to get the campaign up and running, adding in new factions as you go.
In other words, at least for the moment I'd suggest not aiming to fill all slots, but working on (and finishing) about two essential new factions and taking it from there. That's already a lot of work.