Blacklists don't work well.
"The cartel" could make their code have a flexible mechanism, distributing "approved" donation addresses among their members (pools, exchanges etc).
6/
One possible BU defense would be a further SF to restrict CB outputs to a address, but I'm sure you can see how that would be another bad move (think existing donations & optics).
I opened another BUIP, it would ask to release a May version that contains any non-controversial updates, but simply not include orphaning based on some involuntary CB payouts.
makes sense to make it explicit but to my eyes this come bundle w/ blacklisting. You basically introduce a precedent and remove plausible deniability when it will be most needed.