I am SO thrilled about all the awesome Pokémon on the early routes!
My Black 2 team (w/ nicknames!) is currently planned as follows:
Nickname * Pokémon - Reasoning
Emile the Serperior - Azurill and Growlithe were must-haves from the get-go, so I had no choice but to designate Snivy as my starter (and because I'm giving all my 'mons nicknames, no I will not be replacing it at any time with another Grass-type).
Devin the Azumarill - "It's so bouncy and round!"
Gian the Lucario- Need I explain?
Brax the Arcanine -
DAT BITE
Rodri the Magnezone - Needed an Electric-type somewhere, and it's probably the only way I'd ever get past Roxie's Gym, considering my starter. XD
Eriel the Flygon - I
wasjust gonna have an HM slave named STEVE, but then I noticed Trapinch was
actually available in the Resort Desert (eat your heart out, Elesa!) and Vibrava/Flygon get Fly. :3
(If you can guess the naming scheme, I'll give you a cookie!)
EDIT: @gliscor&yanmega, You're most certainly correct! Any Pokémon can be traded over once trading is possible, regardless of whether or not they're in the regional dex; I recently did a run of Black version with all-Hoenn Pokémon.