Hi there!
The feature has been added, thanks for the great idea and suggestion!
The limiter settings were moved to the maps tab, so they can be changed on the fly during a game.
I'm just now realizing that you won't see the update if you are on Factorio 2.0 and not 2.1. I released an update to 2.1 a little while ago but I think that it just silently doesn't show up for 2.0 players. I'm not sure if I can publish a second version for 2.0. But let me know if you run into issues?
Also finally released a 2.1 mod to make copy/pasting parts of the base with mixed qualities easier, if that's a problem you run into: https://mods.factorio.com/mod/quality-gardener