They just removed entirely the tax on standing capital (only real estate will remain taxed), and more could be following. To me, the government is taking Brexit very seriously and is intent on making the most out of it; including producing new legislation to attract businesses relocating out of London.
Bankers not only have Paris fighting to have them, but the whole government as well.
however, if they all end up in one place, that would be a significant long-term threat
If I would not hold the German black belt in suppressing my emotions I would have laughed uncontrollably.
(Though compared to the trains in the U.K...)
I wouldn't be surprised if some kind of local government agency in Paris was helping expats with paperwork, but the idea that all French civil servants and forms will suddenly start speaking English seems outlandish :)