Air-to-water heat pump + underfloor heating + controlled residential ventilation with heat recovery - individually room differently temperature controllable?

Do you think it would come to that?

No. Probably not. Only IF there is mold somewhere, then there.

Allegedly, the scientifically determined ideal temperature for falling asleep is between 16 and 19 degrees.

That is probably rarely achievable for half the world’s population without air conditioning. ;-)
So: I’ve heard that too, but I no longer know anyone who actually has 16° in their bedrooms. We have 21° all year round and we find it much more comfortable than the previous summer-winter fluctuations between 18 and 28°, which we thankfully got rid of thanks to the heat pump and air conditioning.
I would say you get used to not being cold when you get up very quickly and then enjoy the new building. Times just change. For the better, as far as living comfort is concerned.

Allegedly, the scientifically determined ideal temperature for (falling) asleep is between 16 and 19 degrees. So I would like to have the temperature in this range. The problem, of course, is that the body loses a lot of moisture, and that should not stay in the room for long. Therefore, one should not turn off the controlled residential ventilation, I believe.

I would simply turn off the thermostat in the bedroom but keep the controlled residential ventilation running. The controlled residential ventilation only has heat recovery (usually around 90-95%), but it doesn’t actually heat. For every complete air exchange, you still lose about 5% or so with controlled residential ventilation — and it has quite a bit of throughput.
We have such a setup running here — even with (crazy!) air conditioning working against it.
From our recent experience over Easter, when we were away, I can say: rooms where the thermostat was turned down definitely become a few degrees cooler than the others.
We always have the heating turned off in our office. We have hardware running here all day (4 monitors and various computers) that produces so much waste heat that you don’t need to heat the room in a well-insulated new building.
But if you are away for several days, the office cools down quite a bit, despite the controlled residential ventilation running. :)

For those who want to read more on the topic, I just found another thread:

I have to ask my home provider about that.

You don't have to ask anything: just turn the outlets. But a controlled residential ventilation system is not responsible for temperature equalization, that should be added.

The controlled residential ventilation systems offered simply cannot achieve this because the throughput is just far too low and air is a poor conductor. With such a controlled residential ventilation system, fresh air can only be continuously brought in and moisture removed (maintained at a certain value with an enthalpy exchanger and adjustable bypass).

Even the often touted pseudo "cooling" of the controlled residential ventilation system is a sham because nothing more happens than the system simply blowing the room's exhaust air directly outside (without first passing through the heat exchanger). However, the then "cooler" outside air cannot cool due to the low air exchange rate.