Few thoughts.
It's not uncommon to hear of passengers who work in Paris but actually commute from home in Bordeaux by train - there is a certain movement about quality of life that big cities don't offer. Fun to visit them but they have their detractions too. I realize it may not be ideal for all, but for example are there no high speed lines from CDG to Bordeaux?
AF doesn't even fly to Brussels - everyone takes the train at CDG2 Grand Lignes station instead.
Someone must have the stats for % connection passengers at CDG v KL/BA/LH/LX etc - but out of NYC we connect many people to the regions in the UK, all over Europe, the Mid-East and West Africa as well as France. And we have AMS just up the road. I think some environmental stimulus to reduce our carbon footprint from the Government is amazing, and this is an opportunity to speed up our efforts. Wish our Government in the USA was as enlightened!