In the Species1>Complex case, I see no problem with it as long as the curator who downgrades stuff also has a duty to take proper care of the results, in a timely fashion (in a matter of hours, not months). In essence, it would make theoretically (rather than technically) impossible to downgrade 1600+ obs from Species to Complex, unless the curator properly organizes a “re-ID task force” beforehand.
Anyway, same old, same old. If only there weren’t outstanding feature requests aimed at alleviating curation issues… improve guidelines (RFC-like?), technical safeguards (e.g. hands-on experience of curators, automatic delay, mandatory notifications before any commit, etc.)