All part of the anti-Parliament, anti-parties line on which the constitution was written.
But, broadly, Parliament's powers need increasing relative to the presidency. The PM and major ministers should be deputies, not just presidential appointees.
I think really major changes would require a referendum.
See Wikipédia (French).
(Not a query concerning girth).
Particularly when it is "convention, custom and peer pressure" that is the main defense against abuse. As we've seen in the US and the UK a determined, media savvy government can run roughshod over such implicit restraints.
