Driver Overlap Fix
Now that you offer three drivers (legacy-1, legacy-2, and current). This idea would help debug and maintain things better. It applies to both Windows and *nix OSes.
The driver forks should not overlap.
Incremental driver versions of one fork should not overlap.
The xorg.conf should specify the driver it wants. Examples:
where x,y = real version numbers. (You could do some graceful behavior if the old "nvidia" is used - make a guess based on what is installed.)
Many people run from USB sticks, external disks, or live CDs. They move from machine to machine with the same OS and drivers. If the two machines have different cards, they need two drivers within the OS.
But even if the cards are the same, or the machine is, two drivers can still help debugging.
You want the user to test two versions of your driver. This is painful because it involves uninstall/reinstall/reboot. Properly versioned drivers let both be installed. The user can report results of each separately. It should be possible to have both 7123 and 7124 installed on the same PC.
Sysadmins sometimes do OS installs with direct partition copy from one disk to another. That's another reason to want multiple nVidia drivers without overlap. It is possible to install all 3 nVidia drivers in the OS and not worry about anything but one xorg.conf line.
Finally proper versioning would help Linux distributions. They would not have to worry about overwriting old drivers. In fact the recommended advice would be to keep the old one until the new one is verified to work. Then uninstall the old.