Your suggestion is pretty bad for the game, because it would make drones immune to any damage and they could not be destroyed anymore. Your reasoning “would negatively effect small gangs” is just a tip of the iceberg… You could use invulnerable fighters to nuke keepstars off the grid (just launch the damn things from extended ranges and watch them chew the keepstar in pieces…)
There are better (less crippling to game mechanics) ways to reduce server/client load, for example I posted this thread while ago with some suggestions about it: TIDI 2.0 (those would leave normal non TIDI gameplay 100% untouched and only affect these big lagfests…)