Thats up to the championship promoters and riders to sort out, not the PL promoters

No imo. If the PREM collapses then the CHAMP collapses too and clubs like Glasgow and Poole will have to open the cheque book anyway because current CHAMP HL's as well as British League D/UP's will demand much more money to cover a loss of income. It's a benefit to everyone for British Speedway to have 2 Main Tiers but 2 Main Tiers is only possible if powerhouse clubs are willing to put the Sport first instead of themselves. Unfortunately clubs don't operate like that over here, Hopefully one day they will but the Sport as a whole hasn't come first at an AGM in years.

Yes maybe possibly surely hopefully, any of these 

Better than sacrificing two well run like Poole & Glasgow to keep the PL going

Won’t be any of the above, close but not quite. 

However ... The Championship only pay rates they can afford due to doubling up.... Championship HL's will want (at least), double if they only have one job... Would the Championship stlill be "OK" then?