Hey Gang,
this is bugging me for quite a while now, and although I know why we put the restrictions there back then, I'm not sure the benefits still outweigh the problems.
Especially now, when we'll probably be getting some traction, I'd like to propose removing the type-check completely. On top of that, we could have some "known" types (koji_build, bodhi_update, compose, ...), and implement a "spellcheck" - like a Hamming or Levenshtein distance - to catch typos, and warn the user.
All the Taskotron jobs are given the type programatically now anyway, so the worry-for-typos is now IMO a bit lessened, and actual human users would be warned in the logs.