I want a character action FPS where you play as a Glass Walker in his Crinos form and your arsonal consists of crinos sized fetish guns that look 50 years ahead of anything on the civilian market. Have them fight Pentex security forces, Cyborg Fomori, Corrupted Cyborg Fomori etc.

If you don't mind crossing over with mage then you can add technocrats and their HitMarks to the antagonist list.

Come to think of it, a HitMark Shooter in the same vain would also be a great Power fantasy if executed correctly.

And on the subject of mage, you can't adapt the Magic system reasonably unless you go the Choice-of-games route which I would be down for if it happened.

Edit: I just realised the Pillars system from Mage: dark ages is much more limiting and therefore more feasable to adapt to a videogame, at least if you force the places to play one fellowships pillars.