I'm only speaking off my own experiences, but Fox will always go for FD or Town and City first, those are his preferred stages. Following them are either BF or Smashville. Take him to Lylat if possible.
Also, if Fox can kill off the top easier than his opponent can he'll probably opt for Delfino or Halberd as well, but those stages are high risk/reward since Fox is fragile and his recovery can lead to him missing ledges or getting Halberd'd. Duck Hunt and Castle Siege are just there, though the ducks can mess with his blaster and the dog can screw with everyone.
So ban FD and Town and City and make Fox think carefully.
I'll be honest, I'm not experienced in Fox customs so I stuck with one set the whole time. You already know Twisting Fox and 64 Blaster, but other options include a charging blaster (3) that has obvious startup but big damage and knockback, the Wolf side-B (3) that spikes at the sweetspot but has less horizontal range than his normal side-B, and an up-B (2) that doesn't have a hitbox but gives Fox more flexibility when recovering. Also, Fox can gain extra height off jumps by using fair during the ascent, can stall in the air with any Reflector, and can use Reflector to change the direction he's facing. If you plan to use any characters with a projectile, Fox can escape reflect-lag by rolling, spotdodging, or jumping.
Do you have any secondaries you might consider using? :O