Hi Chris, I see one main problem with this design. When you go to pump out the reactor the pump will stop before the reactor is drained. Also it will prevent the pump starting when you want to pump in your next batch of oil.
But having such a design only on the heating circuit seems logical to me.
In practise however, I don't see a need for this extra complication, because I find it only necessary to heat once. After that during the mixing time no further heating is required, so I then unplug the element. However, if you are to be constructing reactors for other people then it would be well worth using in the design.