The typical age of a house in a model park is around 10 years. In the case of the TE's property, it was a house from the 1980s.
As of now and today, there is a very significant difference regarding the materials used, insulation, thermal bridges, windows (insulation, glazing, burglary security) and much more. So there would be a lot to do on the property from the beginning of the thread. You also need completely new insulation; the old one certainly would no longer be installed after almost 40 years! And moving the windows, unless they have already been renovated, would really be a lost cause.
Houses from the parks are indeed often sold. Mostly – according to my information – however, to factory employees. They then also have access to the necessary resources and expertise, machines, all plans, and much more. And not every manufacturer sells their model houses. Some go "directly to the scrap yard after their life as a model house ends."
With a 10-year-old house, the "move-and-pimp" is certainly more feasible. But as already said: The new setup counts as new construction. Thus, all requirements must be met. With a house older than 30 years, I consider the project financially and technically doubtful; I even claim it is purposeless. I have made alternative suggestions to the TE. See above. The house, as it lives and breathes in its place, has its value since it can be assumed that with good maintenance it will last another 50-70 years. In my perception, moving/dismantling would be destroying value like no other.
Best regards Thorsten