I'd be VERY surprised if it's true that AMD recommends compatibility contexts.It's why Nvidia is trying to bring OpenGL to Android and why they still recommend using the compatibility profile for new OpenGL applications (I also heard amd recommends the same? not sure).
The interactions between newer (core context) and legacy (compat context) features range somewhere between completely undefined and batshit crazy. For that reason alone mesa does not (and most likely never will) support ARB_compatiblity.
Sure you can make it work somehow - it should be ok if you don't actually mix new features with old ones "too much" (so, only mix things which have at best "obvious" interactions).