> * a master that now is frozen,
> * branch with everything needed merged, continuously
> * feature branches that contain one and only one new feature

So, we could make something like

master
active-development (testing everything)
active-development/feature

And when a feature is mature enough (aka merged into active-development a 
while ago and tested) it can be merged into master?

Sounds ok

-- 
Money can't buy happiness, but neither can poverty.
   -- Leo Rosten