Junkyard and Film studio are the most balanced bases, if we let teams choose their own they'd choose ones that aren't balanced so as to try and give themselves advantage. A couple of us on irc have discussed it and decided Film Studio and Junkyard are they two most balanced and suitable bases.
Edit- As Junkyard has 2 entrances, 1 of which you can get a car through and Film Studio has 3, 2 of which you can get a car through, we are going to block off the far road entrance of the film studio.