You're supposed to install drivers in the C:\ drive. Windows isn't going to look for where you put your drivers other than its designated spot.Not true. You can point, direct and redirect w7 to wherever you want things sent and retrieived. It just takes a little time, insistence and patience.
Well, I'm sure you could also just symlink the INF folder. Either way, driver and support software usually doesn't take up any more than 100-200MB. I'm curious as to why OP is so concerned about saving space on an SSD. Especially with system files. The point of an SSD is so your IO is faster, especially with system files.