IMHO the main house and the outbuildings should be complimentary or contrasting. You could design the new workshop/apartment to be in the same style as the eventual house, or completely different but in a non-clashing manner.
For instance, our house is white with red doors and a light red roof, and looks like a house. One outbuilding is the same, the others are all red with white doors, white/light roofs, and look like barns.
On an aside, is a bunch of men arguing aesthetics another symptom of the Winter doldrums?