While I agree with your sentiment, it’s not in the cheating section, so it isn’t technically cheating.
Skill rust capped at level start seems to be the fairest option anyway.
Although I would like that as default, but with the first % being harder to achieve. That way it’d feel more fair for me. You don’t lose your level (so recipes aren’t locked), but progress is more difficult until you “get the hang of it” again.
It would also work well with the way crafting works as default. Until you have over 20% the required minimum level there’s a chance of screwing up and lose materials. Making harder to get that 20% would balance the fact that you can’t lose a skill level anymore.