Why not have both the SBK and MotoGP in one unified championship? The displacement discrepancy is so close it's negligible, the riders are stacked well, and about 2/3rd of the tracks in the MotoGP circuit also host SBK. And even better is that Dorna Sports owns both franchises. There can also be three 12-hour endurance events set in Old Hockenheimring (which Hermann Tilke wants to keep alive, apparently), Bugatti Circuit at Le Mans where Moto24hr is held, and Nordschleife.
Or, if that isn't a good idea, have a unified race format in which both leagues race in one track, but there will be different titles. MotoGP would be like LMP1 because they're bespoke machines and have the SBK as the GT1-like class since they're race-prepped production superbikes. There will be different titles, but any rider from SBK can get to first place overall, ahead of a MotoGP rider.
But neither is a good idea, so I propose just the three 12-hour events where both leagues can race together; just replace old Hockenheimring with Imola and Nordschleife with Istanbul Park.