The issue isn’t whether you reduce payload but the max fuel tank capacity. Even if you take passengers off, you can’t get more fuel on as the tanks are full.
For a 757, IIRC the tank capacity was 34.4 tonnes. With a burn of over 3 tonnes an hour and diversion fuel, contingency and final reserve, you can’t fly for more than about eight hours and potentially less if you have a long alternate.
The 321LR burn will be better with the newer engines but tank capacity lower?
I cant see this thing making it to Orlando from Stansted. It’s a 9h30 airborne at an A321 cruise speed and if MCO is forecasting afternoon TS activity then SFB is no use as an alternate and you need fuel for TPA or MLB. I don’t know the aircraft well but I can’t see this working.