There is a danger in having retired popes. They can still use or be used by their former status as the reigning pope.
We have seen this tension in Pope Benedict's retirement. Perhaps he doesn't like the direction of the Church under his successor and has made veiled points about it in his writings and meetings with various people.
Or others use him for their theological and ideological purposes. Pope Benedict's recent visit to his homeland to go down memory lane with his dying brother (let's face both are dying) was used as a diatribe against the reigning Pope Francis, all fantasy of course, or is it?
What if Pope Benedict leaves a testimony after he dies that calls into question the papacy of the reigning Pope Francis.
Thus having retired popes can created division and schism in the Church.
We have been living through the "Benedict Option" or should I write "experiement." It is an experiment in the retirement of popes. What has it told us and should this experiment be institutionalize do or abolished?
If popes remain for life, we will be dealing with an incapacitated pope, similar to Pope St. John Paul's last years and months.
If a pope has a debilating stroke but a healthy body, he could live for years in a totally vegetative state. The same with demential or Alzheimer's disease or other diseases of that type.
Is there a way to have a "Vice Pope" that is simply a caretaker who makes sure that the Curia does it job without overstepping their purpose?
Should popes have a retirement age or should they remain for life no matter what?
And what can be done with a pope who goes crazy but is not incapacitated. Should there be canon laws to deal with a rogue pope who might be a heretic?
Or should we just trust the Holy Spirit who eventually uprights the ship that lists?