Firstly: GSX is a fantastic product that adds a whole new dimension of realism to FSX. Amazing, amazing work!
I apologize if this has already been requested -- I did a few searches and couldn't come up with something. Would it be possible to give an in-game option for selecting the livery to appear on the ground vehicles as an override for what's set in the scenery? This would allow the user to, as an option, select a livery that matches the airline (or just leave the livery that is set in the scenery). I know many of the scenery updates I use are correct but a few are not. Ideally, this option would be part of the GSX menu so one does not have to park or access another menu to make the request.
I recognize that a list of all liveries might be excessive so there would have to be a way to pair it down. I have had a few situations where selecting the same gate gives different liveries because the gates are shared between carriers. Perhaps the user could get just the options available in the scenery. Or maybe the full list that you scroll through only if you don't like what the default scenery option gives you.