Can't offer any Airbus comments .. however .. the MEL is not a system for permitting cavalier continuation of flight.
The basic philosophy is that the aircraft Type has a bunch of kit necessary for certification .. ergo, if a bit of kit is broken, the aircraft is unairworthy.
That's all fine and beaut .. but, in the real world, it is not very workable unless you are a well-heeled private operator who doesn't really need to fly unless everything is gold plated.
Therefore, the gurus have a think tank and consider a range of broken kit .. with the aim of determining what additional limitations, etc., are appropriate for flight to continue while maintaining something akin to the basic certification risk profile. As a simple example, if a cabin item doesn't function, there might be some limitations imposed on passenger operations. At the end of this process, we have the MMEL, authorised by the certificating Authority with the OEM's blessing. The MMEL then is modified to address any specific hull and local regulatory requirements .. when this is finished the local Authority approves the modified MMEL as the operator's MEL.
The important thing to keep in mind is that the MEL addresses intentional operation with a bit of busted kit and seeks to maintain the certification risk levels.
It is a different matter when something breaks after despatch .. in this case it makes sense to have a look at the MEL to see what considerations might be relevant for the Commander to take into his decision making process. However, the inflight situation is managed as a one-off risk control and mitigation situation.