Having been in the injection molding industry for 30 years, my biggest concern with polycarbonate mags would be chemical resistance. That has always been the Achilles' heel of PC. That's why you almost never see it under the hood of a car. Polycarbonate would almost be the perfect plastic if it had good chemical resistance.
Nylon has excellent chemical resistance, and that is one reason that you see it used for under-hood applications and most pistol and rifle accessories.
Additives and modifiers continue to improve, so I'm not saying that a suitable PC doesn't exist, but I would be careful with getting any kind of chemical cleaners and lubes on them. I assume that the clear and smoke Lancer's are PC, and I haven't heard of them falling apart. They wouldn't be my choice for long term planning however.
ETA - After some more research, the Lancers are probably PPSU, which has excellent chemical resistance but is pricey.