IIRC, Kelly has tried to put his QBs under center several time since 2010, but it's never worked well. Apparently the differences in the QB-C exchange between shotgun and under center are significant enough to have caused Rees and Golson serious problem-- as in, ball on the turf/ drive killing type problems.
I'm hoping that Kelly and Sanford emulate Meyer's late 2014 offense by incorporating more gap-blocking elements into our rushing attack, which should mean significantly more practice reps with Zaire under center and Luatua playing FB.