The talk is that the French will relieve the Ukies on the Belarusian border. That frees them up to go to the active front to fight the Russians. This also put pressure on Lukashenko in Belarus. He would then have the Poles to his West, the French to his South, and possibly more NATO troops in Lithuania and Latvia. The Belarusian people might depose him in that situation.
NATO troops in the Ukraine will be fair game.
If France puts its troops in Ukraine expect Russia to do its best to kill them and rightly so.