For those of you questioning the fulcrum/anchor-point, I think that's why OP suggested firing at a 'roid.

The warhead would latch itself to a rock then fire out beams to tether the target ship(s) and use the rock's mass as a counter to the ship(s).

On this basis, you could alternatively use it to tether two target ships to each other for some gimmicky effect.

I think trying to codify any BR/Boost effect might not be worth the effort - just apply Agi penalty.

Did these for a contest a few months back. Wraith Squadron books for the source.

For context, in the books these things used some kind of gravity well projector to drag ships out of hyperspace, then smash them with an EMP/Ion effect. So kind of on topic...