Hi Karspars,
I found your project when researching
Daikin Multi Plus:

https://www.youtube.com/watch?v=NDQLXsfA6r8

Initially, it looks like the perfect solution for me and appears to be the same idea as your project.

A multi-split “air to air” outdoor unit with a water cylinder heated via refrigerant lines.

Unfortunately, I can’t find anyone actually selling it!