Interesting suggestion !! Could tie into the idea I presented here:
I don't know if an RPG angle would work. You'd have to elaborate on that.
I think OJP is somewhat versatile enough to do whatever you want. So dedicated forces of TLS and TDS can just slug it out in a FFA or TFFA game type. Or in CoOp like you did on Hoth...the armies of Reborn swarming at us ROFL !! Would have been coolz but for the lag.
My suggestion would be to see what you can do with the current OJP revision, make notes of what you think could be added to enhance your idea, and present them.
Sufficient player organisation would mean MORE players LOL !! I'd concentrate on encouraging more people to OJP first of all. Who knows, they could also add to your idea which could thus benefit all.
Good idea though...