I think if the 6 Premier league teams had left, this could have been a thing. But now that's not happening, it doesn't make sense.
If 6 teams had left it would have been a sort of "damage control" phase for the Premier league. How do you replace 6 teams?
One way to do that could have been to add some of the Scottish teams and you could do that without the normal promotion and relegation.
I think if the league was down to 14 teams, you could add 2 Scottish teams and 4 championship teams.
You could even go further and add the top 6 from SPL into the EPL, I'm not sure outside of the top 2 in Scotland the others have a global draw.
As it stands, with the 6 staying, it makes no sense to add the Scottish teams. The Premier league is a strong league and the argument will be that the Scottish teams have not earnt a place in the Premier league