It would be great to see and I would like to see it, but it's all pie in the sky, until Poland can be persuaded to release riders. And there would be hell on, if one of "their riders" got injured on international duty.
Good god no. An injury to a rider and you have the same pair of riders out in every other heat.
One league will also have a huge diversity in the standard of riders.
And playoffs keep seasons alive for more teams.
Try getting riders to leave their Polish clubs for the weekend and getting all the other tracks in Britain to cancel their fixtures on a Bank Holiday. Good luck.