I think your samples look vaguely European. In Europe, hell in Normandy alone, styles could vary a lot. So I think you should offer a lot of options :-)
Like in this one you have brick partially with render and those wooden frame rendered walls:
Traditional buildings in Normandy by
EIL Intercultural Learning, on Flickr
Here is plain stone, probably more common on farm buildings like that modular warehouse:
If you remember the old Mordheim buildings (I still use them for WW2 skirmish) their way of affixing corners with plastic stonework would work with plastic walls as well. Is that how you are going to assemble the buildings? But I think your corner stones would need to look more uneven, sort of like this:
(Link to the page if the image doesn't work:
http://www.bugbitten.com/photos/Europe/colleenashfield/Brittany_Normandy_amp_Paris/2431-342-73914.html)
So Stone, Brick, Rendered walls (some damage with stone or brick underneath), plain brick, with bigger alternating corner stones. Seems like you get more and more stone and brick houses when you go north into Belgium and Holland. But I'm no architect...
You also get some thatched roofs in Normandy and Belgium too.
Here's a lot of information:
http://en.wikipedia.org/wiki/Architecture_of_NormandyThis blog post is very nice:
http://belgianpearls.blogspot.se/2011/01/belgian-architecture-and-interior.htmlI'm not sure going fully modular is the way to go, maybe a modular series combined with one-offs that are more quirky and characterful.