Unless you are hyper concerned about the loss of glass with an insert application, I don't know that ripping out all the trim is really justified. Setting the windows inside the wood buck frame is easier to install, seal, trim the exterior, and cheaper (i.e. no interior trim charges).

I agree with WoW. The other issue you may run into by setting to the brick is that it may make the interior of the window look odd since so much of the frame will be covered the interior returns.

Thanks for the replies. The house is gutted so all interior trim is already gone. I was concerned that the windows might look odd from the interior if they were installed on the brick and not the wood framing. It looks like I may have to keep the brick mold. I was trying to eliminate the brick mold and have as much glass as possible with narrow frames.