Only update once evey few months and it's more bearable to redo a lot of things from scratch IMHO.
I'd much prefer a solution for that controller not saving thing, which erases your mappings if you carelessly unplug and forget to set a cfg on read-only (for which having to do that is already by itself a very bad thing since it locks other useful settings) That has to be the one most absurd and infuriating thing in MAME useability-wise. There's a page about stable controller ID in the docs but it's mostly hieroglyphs and I don't even know if it's describing an actual solution or an ancient cooking recipe.
Dealing with a fresh new MAME install is much les bothersome than having regular fights with the one you already have, methinks.