Is there some way to implement a way to dismantle behemoths? It wouldn't be instant; I'm picturing something like how citadels work now, where it takes a few turns to "build" (or in this case un-build). During this time, the behemoth wouldn't serve any purpose; no bonuses to FIDSI etc. would be accrued, no actions could be taken, it can't attack or defend itself (or move, obviously) and citadels wouldn't provide any of their bonuses to defense.

But an enemy fleet with weapons could still attack an un-escorted behemoth & automatically destroy it as if it were a civilian vessel. And until the behemoth finished dismantling, it would still count against your behemoth cap. Also, for the purposes of balance, I'd be OK with there being nothing to reclaim once dismantling was complete (no Dust/Industry). I just want the darn things GONE.