I think the match FA Cup game in which Theo played up front was one of our most fluid performances of the season. When there is a lot of movement and interchanging up top is when we look most threatening. Unfortunately with Giroud it can't happen. Incidentally Theo got injured in that match, else we may have seen him play there more in the 2nd half in my opinion.
I wouldn't be averse to the idea of Theo up top if we can get in a player of the quality of Sanchez.