I'm not sure that there will be co-op for SP. I think it's going to be an MP feature only - a bit like team deathmatch or something similar. I've re-read what was posted, and that's how it seems to me.
As far as the films go, my favourite is ESB because it was more varied and grittier than all the others. ROTJ was okay, but they had three battles going on at the same time, which I felt detracted from the story somewhat. It was a shame they decided to do the same thing for Episode I. No doubt they'll do the same thing in Episode II (although I hope not).
A major battle and a duel would be more than enough for the finale...just like a lot of the old movies, such as Robin Hood etc. They worked well. ROTJ and TPM didn't.
I'm hoping they bring back more of the sarcastic banter in Episode II as well, and focus less on the slapstick humour of Jar-Jar the Gungan Menace. :P