Building land in the middle of nowhere with the house prices?!

There would also be the alternative to downsize. Remove the double garage and possibly the basement.

Guerilla does not sound good and in the long run is not effective and will not lead to comprehensive success. If you want to set binding standards that everyone must use, then it has to be issued centrally by an official body. [...] You also cannot obligate anyone to use these materials as long as it does not concern an official body. [...] For the overall organization, the benefit is rather doubtful to harmful, because it will greatly disrupt the implementation of a central organizational unit by the Ministry of Education. Keyword: disruptions in change and acceptance management.

In a federal republic with sixteen states whose election periods are not coordinated, comprehensive standardization is tantamount to a delay in time to market on the scale of two decades [as a reminder: in a blind spot lasting "two decades," one loses one and a half complete generations of students]. The product of the depth, distribution, and introduction time of a standard is a constant, according to my experience in organizational consulting and political practice. And a binding obligation to use it here would override the federal and subsidiarity principles. That Nida-Rümelin was not given the same powers as Goe**els once had is intended by our constitution (and is explicitly welcomed by me).

And even if the participants and their teaching qualifications are known, I doubt that the material they make available automatically corresponds to current scientific findings and is methodologically perfect. [...] And thereby, the effect achieved for individuals is certainly great, because they benefit from the materials. For those who are the opinion leaders there, it enormously boosts the ego.

The other participants are mostly professional colleagues in active service, and those with better content have more followers and more downloads, which is not controlled by some mysterious "algorithm" here, but each independently thinking teacher at their own discretion. The teachers thereby only save themselves from unnecessarily reinventing the wheel multiple times. Whoever thinks what the colleague has prepared is not good enough: improves it themselves or simply does not use it.

We briefly talked yesterday with our possibly future neighbor, who bought his plot in the adjacent new development area from the municipality with a 3-year building obligation. He wants a 160-170 m² city villa with two full floors and a basement plus a double garage. He is planning with several prefabricated house companies to get offers, and according to him, all come to about €750,000-780,000 turnkey (excluding painting, flooring, and kitchen).
So far so "good," but this causes problems with the bank. The construction costs are too high for the value of the plot from the bank's perspective; the security is lacking.

Thank you for bringing the thread back into the on-topic area, if not to the root – if I understand correctly, your neighbor’s bank is concerned with exactly the same issue as the OP: namely their doubts whether the entirety of the loan security from the plot in the improved state after construction can match the amount to be secured in the event of realization. So the questioned influence here, by me and others, of the municipality’s cautiousness on the feasible building costs. I personally see it this way: if you set only a tiny Klausner cottage on a large building plot like a Ponderosa, you contaminate the value of the plot more than if you place a standard city house on it, even if the plot lies in the countryside. Are you yourself building significantly smaller and/or simpler or with a much better financial profile – otherwise you might simply have to recommend your bank to him?

There is also the alternative to reduce size. Remove the double garage and possibly the basement.

Or rightsizing Neuschwanstein in another dimension.
Possibly the combination of prefabricated house companies versus basement also plays a role.
I am happy to personally take care of this neighbor as well, the ways are known.

In a federal republic with sixteen federal states whose election periods are not coordinated, a nationwide standardization is equivalent to a delay in time to market on the scale of two decades [as a reminder: in a blind spot lasting "two decades," one loses one and a half complete generations of students]. The product of the depth, the spread, and the introduction time of a standard is a constant, says my experience from organizational consulting and political practice. And a binding obligation of use would override the federal and the subsidiarity principle here. That Nida-Rümelin was not given the same competencies as Goe**els once had is intended by our constitution (and is also expressly welcomed by me).

The other participants are mostly professional colleagues in active service, and those with better content have more followers and more downloads, which here is not controlled by some ominous "algorithm," but by every thinking teacher at their own discretion. Teachers simply save themselves the unnecessary reinvention of the wheel. Whoever thinks what the colleague has prepared is not good enough: improve it yourself or don't use it at all.

I do not understand the problem with federalism. Each federal state has its own school system, its own curriculum, and its own Ministry of Education. For example: I would place the experts for Bavarian schools in the Ministry of Education in Munich and have them develop materials for the Bavarian schools.

Regarding your second point, you misunderstood me. I do not question these persons' expertise – absolutely not. I only know from other organizations, including public service, what excesses such unofficial groups develop and how quickly some come to see themselves as unassailable and irreplaceable silverbacks. Then the "followers" very quickly adopt everything from this person, and reflection is omitted. And these silverbacks are not infallible either, especially since they mostly operate as lone fighters and want to profile themselves.

I don't understand the problem with federalism. Each federal state has its own school system, its own curriculum, and its own Ministry of Education. For example: I would put the experts for Bavarian schools into the Ministry of Education in Munich and have materials developed there for Bavarian schools.

Alright, only on a federal state basis. As far as I know, the existing exchange platforms are mostly active across federal states, which at the same time also reduces the problem of the feared hero worship, since the participants are often not "in the same soup" to that extent. Conditions like here (Yvonne, myself and a few others are sometimes read several times daily, then there is a narrow middle field, and the vast majority of participants are rare visitors, eternal newbies, or even one-day wonders) do not exist on these platforms as far as I know.

Thank you for bringing the thread back into the on-topic area, if not even to the root - if I understand correctly, your neighbor's bank is concerned with exactly the same question as the OP: namely their doubts whether the total credit security from the property in the improved state with the building can match the amount to be secured in the event of enforcement. So about the influence of the community's fussiness on the feasible building costs, which I and others have questioned here. Personally, I see it this way: if you put only a tiny Klausner cottage on a Ponderosa-sized building plot, you contaminate the value of the property more than if you put a standard city house on it, even though the land is in the countryside. Do you yourself build significantly smaller and/or simpler or with a much better financial profile - otherwise maybe you should just recommend your bank to him?

Exactly, according to his statement or his bank, the planned construction project is too expensive for the selected building plot/location.

We ourselves built similarly sized from an area perspective with about 170m², also with a double garage but without a basement. 1.5 stories with a 40° gable roof and about 1.25m knee wall. Although we did a lot ourselves and did not build turnkey. I can’t quite classify our built “standard,” but through electric aluminum armored shutters and blinds, air-water heat pump with ventilation, additional fireplace and front door with fingerprint, it could already count as upscale? We selected all companies not only regionally but practically locally. Masonry and carpentry companies directly from the village, excavation company and heating engineer each from neighboring villages. Only the electrician had the longest commute with 8km.

Regarding financial profile, I do not want to stretch too far out the window, since currently with my journeyman wage and my wife working part-time because of the child, we are not big earners. Equity of about €75,000 has flowed in from us.