It is! I hope to have it done by the deadline of end February. Still building, but I have a good workflow now, no more mistakes, got it all under control. A pity I have to keep the buildings as low in MB's as possible to be able to run the run render without problems with all these houses. I can always work on them later for more polys (like window sills, drain pipes and rounded rooftops).
Luca Rodolfi was so kind to build a quite complicated house, but it's no use to me, unfortunately, as it's heavy and not quite correct (for my purpose). Doing it myself right now.