After a few attemps, I managed to have it worked... looks like the problem did not come from my solution, but from the fact I did not increment the bundle version... thus, my solutions were just not taken into consideration.
So, the solution that worked for me is setting the endpoint for the context from my routeBuilder, like :
getContext().setProperty("http.proxyHost",10.100.100.1);
getContext().setProperty("http.proxyPort",2111);
Now, it does work.
Thanks for those who had a look!