@chaley
A
Locked lookup table would prevent additions or deletions (purges of unused) except via the maintenance screen.
The basic GUI (view) would not visually change.
1) A locked (with Lookup) field would need some code changes to:
a) trap/resolve 'Not an available choice' values instead of just adding.
b) disable the deletion (purging) of values with no usage, leaving these for future use.
The current 'Manage x' could probably handle these, otherwise, locked tables.
Adding a padlock to the Icon in the Tag Browser to remind the user which fields a 'Locked'
Locked fields could be configured in Tweaks (similar to Hierarchical fields). Off by default
Basically, this option could be used to prevent the proliferation of things, like: Tags, Author name Spelling Variations