Re: Change the law, then
Well, the French can't change the law by themselves, but they might manage to convince Germany that the European law should have an exception for multi-national corporations that have a presence in the country.
It would be a huge burden for small companies to have to declare taxes in every country, and that is why the treaties were written as they were. But companies like Google already have a presence in every country and are paying taxes on that. For them, it would be absolutely not difficult at all to declare in each country what they earn there. The reason they don't do it is not that it would be a huge operational burden, it's really only because they would pay more tax.
In a sense, my suggestion is a bit similar to the presence laws created in the US to force Amazon to collect sales tax. It used to be Amazon did not collect sales tax in most states, because sales tax on interstate transactions is supposed to be paid by the buyer. Then laws were written to say that if the company had any presence whatsoever in the state, even just a warehouse, then it shouldn't count as an interstate transaction, and the company had to collect sales tax. In the beginning, Amazon tried to only have a presence in a small number of states, but now they gave in and are collecting sales tax everywhere.
Forcing companies to declare revenue earned in the country, in each country where they have a presence, would not affect small companies; but it would prevent large corporations from shopping around for the best tax deal.