The inherent flaw - in my opinion - is not the unworkable system, nor is it expecting 14 "top level" riders to keep their diary free to ride with Arran Butcher and Jack Smith, it's the reworking of the format.
15 heats, 4 riders, 4 laps. 3-2-1-0. 60 seconds. It is the most straightforward format you could ever wish for. The format is probably one of the very few things that (British) speedway has going for it. It doesn't need to be replaced with a three stage act.
If this league structure came into play, I'd immediately make my racenight a Sunday, sign the best of those not riding in Poland, and then watch mercilessly as team after team turned up with R/R and 5 NDL riders.