I think a franchised prem 2 will happen, with or without all the Champ clubs being involved.
No idea whether that will have promotion to prem 1 or promotion from whatever is below prem 2, nor whether any promotion comes with non playing requirements like un-realistic stadia or other nonsense like how many social media followers you have!
When? can't see anything being in place for the 24-25 season given the current massive gulf between the PRL & Champonship.
Not sure I would want to actually be part of such a competition, but that will depend on the details which don't exist at the moment.
Equally I don't think I would want to be part of the URC either (no salary cap, no relegation/promotion, pretty unrealistsic away days, dubious quality & no England players in the team) and I am not sure that would ever happen anyway either.
As for a 28k stadium in Kent & sustainable finance etc, sorry, but in the absence of a competition to play in I can't believe any of that is going to happen either.
So option 1 seems the likeliest outcome IMO.