What kind of backup setting are you using for this to be a problem? It's only going to make a difference in time for one backup.
I can understand why people might not want to install things on their C: drive because of Space issues. But for easy and fast backup? Wut??
I copy the raw filesystem device to a file on my server, compressed. Adding 3-4 GB would add up over time as I don't delete the previous versions.
In any case, right now the C: filesystem is too small to accept one or two more 3-4 GB applications so it would force me into extensive restructuring.
Anyway, I don't quite understand why things other than the raw drivers and startup script have to live on C:. For NVidia drivers that is not the case, the bulk of them goes to a drive you specify. Meta's quest package is the only large thing I have this problem with,