Given that out of the dozen or so "main political parties" he is the only one who wants that, and that when asked about their priorities for the change of France no group of frenchmen put that in their top 5 besides voters of LFI ...

You're absolutely right that there are definitely some people who want a 6th republic but do not vote or agree with LFI, but for the sake of generalized conversation like we're having now they're mostly irrelevant. If it were to happen, it would be through him and his "vision", and as such I maintain my critics.

Beware of what you want for you might just get it.

I was thinking that we needed a 6th republic well decades before Melenchon was known and I think he is a dangerous person.

I am probably not the only one.

I’d add that the mentioned acquaintances apparently aren’t calling for a 6th republic.

Just believe that the country is "ripe for it" because of repeated abuses of the, exceptionally large for a western democracy, presidential powers.

But people have been dissatisfied with that ever since the last constitution was enacted. Including, famously, Mitterrand, who despite his many earlier criticisms (describing the 5th republic as "Le Coup d’État Permanent" [1], which could be translated to "The Continuous Coup") was prompt to fully enjoy those powers once elected himself.

So it’s quite old.

[1]: https://fr.wikipedia.org/wiki/Le_Coup_d%27%C3%89tat_permanen...

Not everyone who supported Brexit in the UK was a right wing xenophobe but look where they ended up.