New ASHP Install

[Solal]

, you cannot integrate them properly with a Japanese unit, because they are looking for an on/off signal as opposed to a resistance based thermistor measurement, so you can't weather compensate

Is it not possible  to fit a bespoke retrofit  weather  compensator controller    with the buffer  in a parallel  circuit  like the way Viessmann  do with  thier Mono-energetic system?
With  the heat  pump interlocked   from   the twin stats  on the   buffer  which track  the compensated set point.