while I'm sure there is an "Ideal"
you just have to go with your players
some of our best games in our Star Wars occured because we DIDN'T havbe the "right" character and we had to work it out amongst ourselves
our crew has no jedi, we have 3 soldiers a scout, a gun fighter and a Noble doubling as a medic and so, many of the encounters we've played (Pregenerated and other) have been fun on our own terms
would we have been better off if a soldier took the medic role?
should we have had a jedi; Probably but they didn't and the road less traveled has made all the diffrence- as they say..
I've found in all instances for myself: Playing, GM-ing or taking over for an absentee GM that more than 6-8 people is Too Much