This is a pretty nice spread for Banette, but I would like for them to differentiate it entirely from other ghosts. We already have bulky physical attacker Dusknoir, bulky SpA Rotom-A/Mismagius, average all-around Drifblim, and fast SpA Gengar - we need a fast physical/mixed attacker.
64/117/65/113/63/103 (525 BST) seems like it'd be the way to go. Frail, yes, but it is fast and hits hard on both ends of the spectrum, and lol trolls Garchomp with that speed. Widen its movepool just a bit and I could see a set like this working:
Banette Evo@Life Orb
Naive; 72 Atk / 184 SpA / 252 Spe
Calm Mind
Brick Break
Shadow Ball
Substitute/Thunderbolt/Shadow Sneak
Basically boils down to enough Atk to 2HKO Min/Max Bold Blissey with Brick Break, max speed to outrun Jolly Garchomp, and the rest tossed into SpA. Sub lets it set up on Blissey, Thunderbolt is for coverage, and Shadow Sneak is nice priority that prevents it from being too easily revenged by the likes of Starmie, Infernape, Gengar, etc. If only...