I'd think it's best to keep it, but if you must eliminate an extra accumulator (as fitted to the inner guard on a CX) and want a very easily reversed solution, take a dead welded sphere and cut through the welded end in a hexagonal pattern, weld the hole in the middle closed (even tap and bolt) and screw it on. It mimics a dead sphere that would other wise just fill with LHM but will give you back the room the sphere occupied. You only have a single piston pump in a GS, so it is then critical you have enough stored braking capacity from the remaining accumulators. If in doubt, don't eliminate it as this braking system is unlike anything with a master cylinder and no reserve pressure means no brakes. You can just get away with all dead accumulators and still have brakes on most of the cars with multi-piston pumps, but the pump is worked too hard. I once drove a Xantia in that state and the brakes worked, but the brakes and pump didn't feel at all happy. Also essential is that the handbrake works!