It will work...
But not the way you hope it will.
First, the 6946 slide is longer than the 6906 slide and will overhang the rear of your 6906 frame by approx. 5/16 inch.
Second (and most importantly), it will NOT be DAO.
It will still be DA/SA except you will have no safety and no safe way to decock it.
Other than those two issues, no problem.