I have a different proposal for handling upgrades:

Clear all upgrades at the 24-hour window in status/fare class priority. That way, last minute DM or full Y travelers would get upgraded in the correct priority. (Bitter experience as a Platinum/full-Y sitting in a middle seat in the back, here)

By doing it 24 hours in advance, 90% of the upgraders would know if they got it and could plan accordingly (select their seats, etc). Perhaps a couple of seats could be held for last minute sale or IROPs and given out at battlefield upgrades, but there would be fewer battlefields given out.