http://www.libretro.com/They do have a TyrQuake-based Quake core, and they do have Mupen64plus w/ Glide64 working through RetroArch with acceleration so I think it is possible. The benefit of Retroarch is its specialized use for controllers (with common controls shared across systems/emulators for simplicity), robust video sync and output code, and its portability (ports often leave out the ASM)
It wouldn't replace the usual version for sure, but ideally could be just a make target with some ifdefs here and there to comply with controller and video output support.
The r_tvMode/r_retroAA stuff i've implemented earlier had supporting this in mind, since its role was for testing the new interface within 'television' situations.
