You have to understand this type of manufacturing and how the tooling works. You cannot do multiple fronts.
Maybe I
have to but I don't. Can you explain?
Seems like it would be easy enough to have a set of standard side walls or even side and back walls to which you could attach a variety of fronts, and a variety of roofs. Attachment points for all fronts would be standard to match points on the side walls. So whether the front is square, rectangle, square with the rounded peak, etc. they'd all attach the same way.
My scratch build structures are done that way. Granted they aren't moulded resin/plastic like yours will be but the principle would seem to be the same.