The contractually agreed construction manager will not be provided by the construction company.

Oh yes, René Benko or others of that caliber were also praised to the skies. And what did happen after all?

A lawyer - whom I would consider consulting here nonsense, however - would probably talk about main issue, secondary issue, proportionality and possibly also objective impossibility

I also do not see the proportionality in dealing with this officially.

Is the company willing to talk? If yes, one consideration would be to negotiate the cost coverage of a site manager of your choice...

I also do not see the proportionality in officially dealing with this.

The proportionality is not given, unless the construction manager is a kind of star in his industry.

What is really upsetting, however, is the matter-of-factness with which some immediately consider this normal on all levels, that the contractor can disregard contractually guaranteed details because it costs him more than he calculated or the timing doesn’t work out...

What is really annoying, however, is the ease with which some immediately consider this normal on all levels, that the entrepreneur can waive contractually guaranteed details because it costs him more than he calculated or it does not work out time-wise...

Well, we have not read the exact contractual agreement from the OP either. Because quickly something is interpreted into contract texts that then cannot be upheld.

Exactly. And without any knowledge, it is immediately said here, "Forget it, the company does not have to fulfill that, it is not reasonable if he now lives in Bavaria." One may have their rock-solid opinion about site managers employed/appointed by construction companies and also consider it the only correct one... fine.

But a contract is a contract, and what is written in it is something one would like to have.

Otherwise, we might as well go back to the (good) old handshake days, when one or both sides only do what suits them anyway ;)

PS:
With us, customers also like to withdraw orders if we guarantee person X and in the end person Y is supposed to come...