I would be happy with something on the scale of old school vanilla AV. That used to be fun and is very lacking in swtor, wz's get old fast if you play them most of the time....
I want to see companions usable too in all world pvp, make them more useful and tactical then they are currently.
Early enough in beta they had WZs with that many players (although not that much scope) apparently, but again they were reduced because of engine issues.
Certainly an AV type map would be a decent stand in for proprer RvR.