The question in the OP is actually quite interesting: what is the risk of flying around without an APU and how does that correlate with the latest spat of incidents.
Was the APU a factor in any of the recent incidents to such an extent that the whole MEL safety assessment should be reconsidered? Contrary to the OP I don’t think the APU was a deciding factor in any recent incidents. Even in Sully’s case.
So, do we need to ask the manufacturer, legislator, regulator, airlines and pilots to reconsider the APU rectification interval in the MEL? Is there an emerging case for this? I doubt it.