I cant help wondering if the new 'training' Enstrom will be an updated, lightened 28A which was a bit on the heavy side, particularly 3 up but if it could lose about 200 lb and be limited to 2 place I always thought it would be winner. We'll see. I wouldnt be surprised to see a Lyco C1A in a much lightened 2place airframe using standard Enstrom rotatables.
We discussed the diesel option on Pprune many years ago and the only options at the time were the SMA and Mercedes automotive derived wilksch and Thielert. None were practical at the time as either too low powered or too heavy.
However Delta Hawk are getting close with their V4. I bet we'll see a viable diesel in the not too distant.