The main thing with glass is that it is only rigid when it has lots of curves, otherwise it needs to braced more than wood. Otherwise, the structural rigidity is suboptimal. I did a spare tire well build up for 2 12s, and after four layers of 2 oz may the tub was bulletproof. So I did 2 more layers, totaling 6. Joining it to MDF was easy, too. I'm not sure whether I'd want to invest the time into a whole wall of glass. You'd want to design it with enough layers, curves, and bracing to handle the subs with no flex, which will be a challenge. More so, the amount of time for the layup of thee closure will be considerable, so you may need a loaner car to run errands in. Also, cost of QUALITY glass components may be a factor - you are looking at epoxy resin, which is stronger but almost three times more expensive. Then bracing, deadening, finishing, and a year's worth of sanding.
If money is no issue and time is of no consequence, go for it! Otherwise, plan carefully, read a lot, and get your supplies from US Composites in Florida - great product and very, very fair prices.
4 Fi SSD/Fi BTL soft parts 12s on AQ2200 at .5 daily;
Focal Polyglass comps/Crescendo CZ65s on JL 300/4;
Mechman 240, DieHard Platinum AGM & Optima Blue top, all KK 0 gauge runs and terminals.