drivers exist on 2 levels. Physically they are in the system folder within the OS, but logically they exist within the registry. So long as you modify the registry properly then you could technically put then wherever you want. Please note though that this would be in the category of 'all time dumb ideas' just to save a few MB of space.
Plus, every time you need to access something in your hardware (which the drivers control) the computer will have to wait, spin up the HDD, find it, and then load it.... this entirely defeats the point of the silent and fast seek times of an SSD.
Look instead into removing things like pre-fetching, disabling (and deleting) the virtual memory (which will save you as much SSD space as you have of RAM, which adds up quickly). Also, move things like your downloads folder and other bulk-file folders to the HDD. These kinds of changes will save you GB's of space instead of the little bit of space that drivers take up, and they are much simpler to move.
If you simply have too much stuff to fit on your drive, and you are more concerned with game loads rather than overall/consistant performance, then do a little research into Intel RST SSD caching. The advantages are not as good as running off the SSD directly, but it can be much simpler to set up and use than trying to remember where you put everything as you will only see one single drive. The big limit here is that it will only cache up to 60GB, which is entirely a stupid arbitrary number picked by Intel. RST could be much more useful if you could use a much larger drive, and use it as a cache for much larger drives or RAID arrays.