When I was still brewing in a cooler I added a pump with an immersion chiller in the HLT tank and recirculated the wort through the chiller and back on top of the grain bed. It didn't take long to dial in the required HLT temp to maintain mash temp. It also allowed me to do a more advanced step mash that water infusion wouldn't allow. You could certainly add a temp controller, probe and thermowell to the design to automate the process. This, however, is more of a Herms system, which uses a heat exchange method vs a Rims system that usually has an electric heating element integral to the recirculating wort loop. Hope this helps.