Is is possible to upgrade the controller?

I've had my SHEM system for a little over a year. One of the issues I have is during the winter months, the pump short cycles quite often.

I have come across a few controllers from RESOL and Caleffi that have a semiconductor relay for pump speed control. The goal of the controllers is to maintain a fixed delta t temp to increase performance.

Can I upgrade to one of these variable speed controllers with the SHEM system? The two questions I have right off the bat are if the WILO pump can be controlled to pump at the variable speeds? And the manual of the SHEM controller shows that the temperature probe on the tank is a NTC10K and the above controllers come with PT1000 probes. Is it as simple as placing a new PT1000 probe at the bottom of the tank? I guess that is three questions!

P.S. Why does the SHEM system use the NTC10K on the bottom of the tank anyway? It seems like all of the other controllers use the PT1000 at all locations.

Mark