A level playing field for all? A nice dream - but it will never happen in Europe. Remember the discussion about to reduce subsidizing agricultural products? Same thing: true local thinking and national egoism rule here, too.
If AF was successful in making Ryanair pay for services at local French airports, hey, they just go somewhere else and make a business there. And they will be received by local politicians with their arms (and the taxpayers' pockets) open wide.
As much as I hate to support Ryanair through taxpayers money, I would prefer any competitor to exercise some self-critique and ask himself the question: 'What's better in their offer than in ours - and how can we learn from that?'.