Beautiful plot of land in the village with more than one corner

After a long search, we finally have a plot of land in our village that we could purchase. However, it has several drawbacks.
(The following part is only for background and not necessarily crucial for my question. It can therefore be ignored.) The plot belongs to the former grounds of a farmhouse estate. This changed owners about 5 years ago. Before the sale, the original owner sold two plots separately between the village street and the farmhouse. After some back and forth, it turned out that these plots, according to the village statute (?), were considered external and therefore could not be built on. However, this was overturned by an amendment statute. The lower plot is already developed, and we could get the upper one. This was acquired by the seller 6 years ago. And that is where the story begins. The neighborhood (farmhouse estate and the newly developed plot below) started a petition and intrigue campaign that even made it into the press. As a result, the owner no longer felt able to build there. He has apparently already tried several times to sell the plot. And now we come into play. Since we definitely want to build in our village, we have to at least carefully analyze all options. So we face the challenge and the obstacles standing in our way (partly hints from the said neighbors).
Briefly about the plot: It has a perfect size of 1400 sqm, a slight slope, great light, and a quiet location. We would also access our plot via the driveway to the farmhouse estate. We have the right of way and utility easement (unlimited in time) for the 120m fortified gravel path.
And now, briefly formulated, what the special features are:
- Electricity and drinking water are already connected
- Wastewater still needs to be developed. An offer of about €17,000 is available. The crux is the discharge of the wastewater. The corresponding sluice is supposedly joint property of the two neighbors and the municipality. A new connection is not an option, as the village street was just rebuilt and will not be torn up again for the next 5 years.
- There are reportedly still lines (drinking water, well water, cable TV, ...) running through the plot to the farmhouse estate above us. These lines cannot be built over or planted on. The drinking water line runs across the entire width of the first 5 meters. The rest dates back to times when mapping was not very precise. This means we do not know exactly where the lines are.

So now I’m slowly getting to the point. Thank you for your patience.
We know both neighbors, though we are not friends. Both have signaled to us that they are not keen on new neighbors. Therefore, wherever their consent is needed, they will not give it. To be honest, we can understand that. However, they are also aware that eventually someone will come, buy, and build. Insofar, with us they could at least have someone they know and could get along with.
The mayor is currently running the campaign to get the discharge permit for the shared sluice granted. This would also be essential for us to buy.
How do you otherwise assess the situation?

What interests me most, though, is how you see the lines that lie on our property and belong to the farmhouse estate? We are concerned that if something is ever wrong with them, the search will first take place on our property and, for example, we would have to open our driveway. The seller does not agree to our demand that he moves the lines to the property boundary.
What do you think, what could that cost?

Thank you very much for your effort :)

The seller does not agree with our demand that he should lay the cables to the property boundary. What do you think, how much could that cost?

What could that cost him? Half of the market value. ;)

Both have indicated to us that they are not keen on new neighbors. That is why, wherever their approval is required, they will not agree. To be honest, we can understand that.

I cannot understand something like that. Always this bullying – the main thing is that they were able to build and now defend an area with words without having the right to do so. That is called antisocial.

What could it cost him? Half of the market value. ;)

I can't understand something like that. Always this bullying – the main thing is they were able to build and now defend an area with words, without having the right to do so. That's called antisocial.

Regarding the first point. We would not necessarily shift all the costs onto the seller. For us, it is more about the risk of unforeseen costs.

Regarding the second point. That is your legitimate opinion. Unlike the other interested parties in the past, so far we have been told openly and honestly where the neighbors see their chance to voice their resistance. Of course, it is annoying, but if they have to give their approval somewhere and actually do not want someone to build there, it is at least fair that they tell us that beforehand.

Are the pipelines to the farmstead registered in the land register / register of charges?

Are the pipes to the farmhouse listed in the land register / register of building encumbrances?

No idea. What would be the consequence or what would that mean?

at least it's fair that they tell us beforehand.

Sure, it is fair when someone declares war before they swing the knife, but that doesn’t make it any more “friendly.”
I always find such a situation difficult. Although 1400 sqm is quite a good buffer in every respect, I know too many animosities among neighbors that, due to unjustified and baseless fixed mindsets, do not exactly make life together/side by side relaxed.
Yes, you have to weigh that up. Some people don’t care about such things, others cannot live without harmony.
I find this “declaration of war” more difficult than the lines, which can possibly be removed or rerouted. The latter you cannot do with an unpleasant neighbor (at least not legally).

Remember, building on a slope makes construction more expensive.
Toitoitoi!