Building on the parents' property

The question now arises as to what reasonable alternatives exist to dividing the property and the associated costs / delays.

Few.

The background includes, among other things, the regulation of §946 of the Building Code - by connecting the house with the (foreign) property, the property owners legally also become owners of the house (which is not good for your financing and so on, because then you (in terms of property law) do not own anything at all - and in legal consequence it can also lead to (contractual) compensation obligations of the property owners, for loss/gain of ownership of the house). Behind this stands the principle of the Building Code: what is firmly connected should possibly not be separated (= demolition), but rather compensated.

Alternatives: This is only broken by partial or condominium ownership among others according to the Condominium Act (which also must be registered and rather concerns apartments).

For houses, a heritable building right according to the Building Code is also an option (basically forms a limited, "virtual," ownership-like right between the property and the house). This is a very complex matter, has many disadvantages, and depends on the individual case - and since it is entered and created in the land register, measurements must also be made, etc.

Principle therefore:

[*]No ownership of the house without ownership of the property.
[*]And no ownership of the property without subdivision (for land register etc.).

Exception:

[*]Heritable building right etc.

And then the use / donation (since according to the TO "provided free of charge") must be regulated... So should only possession or ownership be transferred?
So go to a professional for that.