Given the relatively small number of Panthers that the French had, I suspect it was not really worth their while to upgrade or modify them. Perhaps if they had had a few hundred of them they might have considered it. There is also the fact that improving the primary deficiency, it's powertrain, would not have been simple.
Hadn't considered the small numbers of them. Most of the other ones would have had more available or at least abilities to supplement them in short order if necessary, while for the Panther its a vehicle in short supply and its just a temporary unit without any intent for building more. Which makes the incentive to do any modifications for them lower than otherwise, never mind the problems with the most needed vehicle changes.
Quite unfortunate. I was really hoping that somebody would have been eccentric enough to create some paper plans for putting an oscillating turret on it or something in similar fashion unusual.