Paramount did the new Star Trek movie a couple years back with all new actors. It turned out pretty good. I think they would just need to be careful about casting and acting to make damn sure they were true to the original characters. I notice there is a new Star Trek movie coming out next year.
Also, if they did an Episode VII with new actors, what would you like to see for ships and special effects? Would you want to see everything the same or would you like to see them improve the design to show the guns and such? I think they could do some neat things to the fighters and shuttles also.
Same "generation" of ships as IV/V/VI. X-wing, Y-wing, A-wing, B-wing, TIE, TIE-interceptor, TIE-bomber, etc. I could accept perhaps a 1-generation leap forward, but designs need to be derivative of the above fighters, Correlian Corvettes, YT-1300's, Dreadnaughts, Nebulon Frigates, Victory-class Star Destroyers and such.
I'd be okay with updating cockpit displays, HUD units and things like that. I did notice that Lucas had the prequel cockpit computers much more advanced looking than those of the original series, despite being set 30 years earlier. That's true for both Imperial systems and Rebel, so it's not like people are home-brewing analog computers for black market hyperspace calculators or anything like that.
Though it could be said that the intervening 30 years between the prequels and originals ended up seeing a simplification of computing technology rather than increasing complexity, and the computers in IV/V/VI are simpler and more reliable and purpose-built.