I would make the fight at 155, and I would request a 3 rounder. I would try to fight him like Penn fought Fitch. Tons of pressure, take away his movement and speed.
I'm not sure if that's the right one, but it's what I would try
Head movement, more footwork, stay extremely low and try and outsmart frankie and capitalize on mistakes. He's not gonna KO you or submit you so why not let him build a false sense of dominance and try and trap him with as much power as possible, that's what Gray more or less was doing, with maybe less movement and more Power than BJ could really muster but Gray proved he could put him on his ass with a well timed counter combo, and counter him to the body as hard as you can hit him, aim for the liver as much as possible.
I'd fight like Gray did, just really beyond that finishing the job is the real problem, flooring him and a well timed guillotine is as good as I can come up with unless you can go speed for speed with frankie like Aldo can.
and clinchwork, Benson used some clinchwork and so did ALdo I think. Trap him on the fence and drity him up.
Frankie wants you to battle his technical skills you need to brawl like Cain, Matt Brown etc and make it as ugly as possible
I think it really comes down to space, you give Frankie space to work and he will just buzz around and pick you apart and change levels when he needs to.