After 600 miles in and 3 months on an emtb i am beggining to see the 15.5 mph as a bit of a barrier but i can live with it, after clocking the display on the bike and noticing exactly where its cutting off and when, i would concur your figures would make a world of difference to the enjoyment of these bikes. To be honest 20 mph flat would be cool full stopDe-restriction helps bridge the gap.. Controversy aside.
20mph limit off road, 28mph on road would be the ideal compromise IMO