Reverse proxy to simulate a server in the targeting country and webfaction

Yes, this is certainly possible, but it's not something I would recommend because I don't think the SEO improvement will be noticeable. But if you want to do this, you can. You would use something like this:

1. You would point the DNS for your server to the IP address of a server in France
2. You would create an SSH tunnel from the French server to the Amsterdam server using something like ssh -L 127.0.0.1:5555:127.0.0.1:80 your_wf_user@webNNN.webfaction.com
3. You would configure the French front-end server (such as Nginx) to use a proxy_pass directive to forward the request to 127.0.0.1:5555 which will then travel through the tunnel to your webfaction server.
4. You would create a Custom Application (listening on port) which runs on the WebFaction server listening on 127.0.0.1:6666 (modify "6666" to whichever port is assigned by the Control Panel)

Then, in order to ensure that this SSH tunnel is kept alive as long as possible, you would use both autossh and a watchdog script together.

Again, I personally don't think the SEO benefits would be noticeable, but if you want to do this, go right ahead :)

Hope that helps!