Interesting premise, but it does fail to differentiate
between
"something's gone wrong, stop this person for five minutes" blocks,
and 'punishment'/'cooling-off' blocks. Hmm.
Making it an option on the block page (in place of the "anon users
only" check box would work well) would fix that. When blocking
vandals, you want to unconfirm them, when blocking someone for a minor
bit of incivility, or a 3RR violation, you might well not want to.
It used to be "the most recent n% of users",
and was used to determine
who could move pages. Then we enabled semi-protection, and it seemed
sensible to reuse this definition as the target group. At about the
same time the definition was changed from something based on number of
accounts to a fixed three-or-four day limit, which was roughly the
same period of time but less of a logistical hassle (and harder to
game by flooding new accounts)
Excellent!