Passenger experience counts for a lot in my book, it's the main reason MAN T3 is my most hated departure point in the UK by a loong way. MON's departure allows some degree of breathing space to get the T2 development moving whilst trying to cram less into T2. Watching the arriving SQ A359 a few weeks back sit parked up for just under and hour and still be beaten to stand by company going the other way and a half hour behind them suggests summer peak will be tougher than ever in terms of stand capacity.
So MAN will likely take a revenue hit in the short to medium term without MON's based fleet, but from a customer experience standpoint it's a win-win.