What equipment is for resale value

My opinion:

In the past, people asked about a basement; in a few years, the question will be about a "ventilation system, smart home, heat generator, photovoltaics, etc."
The trend will continue that people usually want it to be comfortable.

In contrast, roof types such as "hip/tent roofs" will also lose their significance .......

I think the question is wrongly posed. Apart from obvious points like location, living/usable area, floor plan, and plot size or orientation, it's more about what one should avoid. In my experience, most buyers, aside from a few key data points, do not have concrete ideas. The houses that are fundamentally suitable are therefore evaluated by the process of elimination, and the one with the fewest negative points wins.

In this regard, there are a number of "components" that, for cost or technical reasons, are no longer changed (or cannot be changed), but which represent a no-go for many buyers (local empirical evidence). I count, for example,

[*]Facade with WDVS
[*]glazed (shiny) roof tiles
[*]radiators instead of surface heating
[*]interior walls made of aerated concrete, Poroton, or other poorly soundproofing materials
[*]ceiling height <250cm

Obvious, overly extensive DIY tinkering by amateurs is also very off-putting.

All positive "special features" are in my opinion too much determined by individual taste and/or zeitgeist to subject oneself to the diktat of resale value in this respect.

One could generally add prefabricated houses / houses made of wood to the list. Even though it is not true and many people appreciate wood as a material in the house, a large part is of inferior quality if the overall house structure is not made of stone.

That is correct, in terms of resale value, wooden houses are significantly inferior to stone houses. Sometimes the discounts are not comprehensible.

You could generally add prefabricated houses / houses made of wood to the list. Even if it's not true and many people appreciate wood as a material in the house, a large part tends to be of inferior quality if the overall house structure is not made of stone.

The house our children bought is such a one... and they especially liked it. I was the first to mention to them that Emil von Elling is a preferred homeowner and known for his half-timbered construction.
They found the wooden ceiling on the ground floor absolutely adorable; now it is white, though.
And that stupid slanted wall between the hallway and the open space was allowed to give way to a straight and right-angled wall – thanks to the timber frame construction!
So: it's not so easy to generalize.

I think it's simply a price/performance issue and an openness of the "actually willing to build" to a compromise for their good money.
In a large house, radiators don’t necessarily bother. Many houses from the energy-saving house era still have radiators upstairs. That's okay, so where's the problem?
You can change the kitchen in due time, break through a wall as well...
Is KfW 70, 55, 40 important? I don't think so, if everything else is alright.
A house is a house is a roof over your head, it's a home for a family. Whether white or gray windows doesn’t matter either, when you take advantage of a non-existent house.
Anyone making a fuss about a shower that doesn’t meet the idea of "but I want a tiled shower" or "I won’t move out of my apartment without a dressing room" obviously has other problems.

Did you read the first post? It's not about what is rational or what someone personally finds beautiful, but about what influences the value due to lower demand. I do not consider either wood or ETICS to be inferior, but in both cases there are larger groups (in prefabricated houses even a fairly large amount) that reject it outright, and that lowers the demand. Is that rational?! Certainly not, but it still lowers the price in the used market.