(re)grinding hardened flat ground blanks as a way to improve ones grinding skills?

I'm slowly (trying) to improve my skill set so I can successfully make knives via stock removal and it is clear that grinding skills are both the hardest to learn and the most important skill to doing good stock removal knives. I've been leaning how to sharpen on a slack belt grinder using thrift shop level knives as a first step towards improving my grinding skills and it's been fun learning how to sharpen that way especially since I can now sharpen friend's knives that I really hated to take to stones *and* give them a nice strong convex edge.

I was looking at some of the knife supply stores and saw they sell inexpensive heat treated 440c blanks that are flat ground that I was original planing to use to practice handle making . Would it be useful both as a way to improve my grinder skills (and make these blanks even better knives) to try to regrind/reprofile them on the grinder. If so what shoudl I be trying to do (besides thinnignthem behind the edge...)

More generally, does it ever pay to convert an existing flat grind to a different grind or is that a dumb idea?

TIA

Yes.

You might find some helpful reading in the handiwork section.