I think you could create a big headache by sanding or filing the headstamp off of your cases!
You may end up with a high primer or you could create a headspace problem!
I have seen cartridges with the headstamp removed!
The guy did his work on a lathe. He would "chuck" the brass and with the cutter, he'd just take out the lettering and in doing so, the case had the same case head thickness as original, but the case head would have a narrow groove in it. This guy used a small stamp set and stamped their new designation in the groove.
Sounds like a lengthy process, but if someone was doing this as a special project, it could be well worth it. You could show off your custom made cases at the range.