Um, bon, something essential here is to gentrify Nanterre.
A bit more of business over there will not hurt.
Giant concessions and construction corporation Vinci is to build their new headquarters over there.
http://www.viguier.com/fr/projet/83/...ocial-de-vinci
That will sit nearby the Nanterre - la Folie station where the RER line E and brand new line 15 of the subway will meet by 2022, I believe.
La Folie intends to be a pretty big node of the overall network in the future. 3 subway lines and line E should get there in the 2030s.
All of this is located behind la Défense as seen from Central Paris.
Here's the site by dougdoug on the French-speaking subforum of SSC.
They're beginning to dig for the extension of line E. If I get this thing, the related platforms of the station will be there, whereas the Vinci headquarters will be across some street.
You get an overview here.
http://www.epadesa.fr/la-carte-des-p...he/groues.html
The la Folie station would be pictured as the red component. In the background is la Défense (almost in a walking distance, that's not far away) and behind it is Neuilly-sur-Seine and Central Paris.