Animations will have to be very good for the trick to look good, if the character looks real but iffy animations or limited animation sequences it will look very odd. Especially timing between switching animations to look fluid for this new look.
Also it will probably scare the crap out of you if games have bugs, like pop out eyes, or teeth showing through lips or what not, i think garys mod used to do some weird stuff with faces back in the day didnt it with valve stuff.
I wonder if gta games will have this tech, wonder what gta 4 and 5 would be like with it, or rdr2.