here is more info on that airframe and the stock 80hp engine
Diamond HK36 TC Super Dimona performance and specifications
I understand the concept, but a motor glider isn't the best example (especially since the prop can feather). I have little doubt that pulse and glide in this plane would simply blow away any cockamamie gizmo designed to automate away skill, and not bother anyone "behind" you.
And I have to think that a second engine (or extra cylinders anyway that can disengage) would solve the problem of right sizing the engine for best bsfc constant cruise and acceptable takeoff/climb power with less weight and size and cost penalty. That is what Rutan did with the voyager.