Jim Kirk: Ryan Reynolds
Charismatic, athletic and has perfect comic timing. Would bring a strong female fan base, I think Paramount were foolish not to offer it to him (or if they did and failed, foolish not to throw big cases of money at him. Beats Deadpool anyday.).
Spock: Daniel Craig
Has publicly confessed to being a major Trekkie, would love to be in a feature film. Pulls the deadpan off beautifully. Has the severe facial features and the droll voice, and the ears!
Leo McCoy: Kevin CorriganI'd imagine he and Ryan would bounce off each other. he has that eveyman sensibility but he's often been typecast as a bit of a doofus, I bet he could do a good job. http://www.imdb.com/name/nm0180984/ Pavel Chekov: ???
Hikaru Sulu: Daniel Dae Kim AKA Jin from Lost. Strong, powerful, yet reserved and courteous.
Uhura: Thandie Newton Gorgeous, seductive, intelligent, purrfect.
Monty Scott: James McAvoy
Has a quick wit about him, funny guy but also fiercely intelligent and has an emotional honesty.
I would also say having The Rock or Vin Diesel as a bad ass Klingon General would be cool.
