I can understand Wandamey's concerns, that this program may introduces wrong expectations to some users. Writing comments like this: "I upgraded your addon and
still getting errors. This addon is ...
"
But we should not forget why dopiate wrote Fast API:
At best ZOS would handle manifests with multiple APIVersion-TAG numbers correctly, not marking them as "out-dated", if one of the given numbers matches the current API.
At second best Minion would adjust the manifest based on the compatibility checklist maintained here at esoui. As it is an extra, external program already.
Only at third best Fast API does what the others should have done already.
I think, its ok as long as the user is always aware, that it is done "at own risk", if the addon is not explicitly marked as compatible.
/edit 1: And Wandamey is right: As long as ZOS does not handle multiple APIVersions, the authors still have to release a "hybrid" and a "up-to-date" version, because not everybody will use Minion or Fast API.