EASA and the FAA are recommended to:
Act to change the Boeing B737 QRH – NNC “Bleed Trip Off” so that a limita- tion of the flight altitude should be taken into consideration in the event of fail- ure of one pressurisation system during flight in the same way as when this is identified before dispatch (Cf. MMEL point 21-01).
RL 2013:03 R1
Really? That strikes me a pretty dumb suggestion. The whole point of restricting cruise alt before takeoff with one pack is to limit risk. Whilst on the ground it is easy and risk free to replan the flight at FL240/250, defer the defect, refuel and depart. The point of being allowed to continue at the planned level in flight is that forcing the crew to descend, reevaluate range, endurance, weather and options in general is far and way more risky than simply continuing, diverting or returning as per the planned profile and conditions.