The RFC has been approved during the meeting. A firm request was to make sure the test would not take an insanely long time as to not annoy developers during SWAT deploys.
The job I crafted only run the extensions testsuite (aka skips mediawiki/core tests entirely).
Most of the implementation is completed now and I will add the job as an experiment using the Mobile team extensions then extends the system to the Language team extensions.
I have enabled the change for core + mobile extensions and announced it on wikitech-l https://lists.wikimedia.org/pipermail/wikitech-l/2015-January/080065.html
Still have to tests more extensions and add a system that let people tests their extension with the others.