a small CDDA mod that currently adds a 0 point-cost mutation called "Rustproof Skills", available at character creation or via the debug menu, that essentially "disables" skill rust. I didn't come up with this myself; it was random-cdda-modder's idea that I just packaged into a standalone mod for ease of use for other people. I haven't been able to test this thoroughly because I wanted to get this out as fast as possible so if anything messes up please let me know!
I hope this is helpful to anyone else who strongly dislikes skill rust.