Samsung are pretty good, they have a fully documented Modbus module that allows you to get lots of data and control all the functions. We’ve implemented support for this in Emoncms:
The nice thing about Samsung is this modbus interface is officially supported and fully documented by Samsung, unlike the Ecodan interface which has been reverse engineered. I don’t have experience of other heat pumps, I believe Vailant units can be controlled via eBus protocol which is documented by the hardware required to use it is not very available.
As long as the system is properly flushed and a good quality magnetic filter and strainer is used, there shouldn’t be too much dirt circulating. I would avoid using a heat exchanger, minimising heat loss is key to making a heatpump work well. Worst case scenario is a pump needs replacing, pumps are relative cheap and easy to replace.