With lots of motherboard mods & Prema BIOS mods, The P150EM's single partially implemented eDP port is ALIVE. The 980 is now free of the shackles of Optimus!
But not without problems... no image on boot, 980 cannot run faster than pstate 5, no backlight control (always on 100%).
With the P5 limitation the best I can clock the GPU is around 825/5010. Basically only really old stuff can see a benefit from direct output that outweighs the 40% frequency drop, so here's 3dm01!
A big thanks to Prema for getting me this far.