Going from a 7 speed to an 8/9/10 speed hub body (Shimano) opens up a lot more in the way of available cassettes and is not that hard to do, a steel frame will cold set from 126 to 130 with little to no problem.

I have done this on countless bikes.

My daughters 7 speed mtb is now a 9 speed, my vintage road bike now runs modern Ultegra, and many a nice 7 speed cassette wheel has been turned into an 8 or 9 speed wheel with a new hub body to give them continued use with newer components.