Definitely, absolutely, in no uncertain terms, please please please, KEEP the switchable greens and stopbars.
I've had the pleasure of flying into LHR, sadly no more as our slots were asset stripped by Big Airways before they sold us down the river, and now LGW, usually twice daily. Fantastic system.
I would say most of us are more than prepared to put up with the odd time a red holds us up for a few seconds, and the rare occasion a stuck stopbar causes problems. Personally the need to marshal aircraft across a stuck stopbar at the hold is a bit O.T.T., but even then the value of the system far outweighs any problems it might cause.
If only MAN would install it, a lot of chatter and confusion would be removed. Not a fan of BA, as you can surely guess a Bacon rasher wouldn't be, but they should concentrate on sorting their own house out instead of interfering with such a world leading idea. Keep the lights switchable!
Oh, and a big thanks to the GMC lads and lasses for their quick work.