The process should have "from" and "to" fields. The "from" field defaults to the title of the considered node with the "Re(^\d+)?: " removed (using the regex used elsewhere). The "to" field could default to the consideration reason so the janitor could remove the extra bits rather than paste, but blank is probably better (display the consideration reason on the form so cut'n'paste of part of it is easy).

"The nodes get retitled and unconsidered" should end "and the one node gets unconsidered", but that should be optional, because you might retitle a node that is currently considered for some other reason, so I'd personally just not unconsider. But a checkbox for such would be fine is someone wants to do that work when implementing this.

The title change should be added to each of the janitorial node histories and a note should not be added to any node contents.

I believe someone has already been testing a retitle feature on the test server.