I was just thinking out loud. It'd mean playing in Goodison up to 2021, a c46k stadium for two seasons either side of the CWGs, and full-capacity in 2023/24. A compromise but arguably the best compromise because you'll definitely end up with a proper football ground.
I just can't imagine expensive movable stands or hydraulics being a solution for a one-off event, and dropping a track into a fully completed stadium bowl would mean the stadium is compromised forever, that's just maths.
Also, dropping the track into a completed bowl would mean a very high platform would be needed if you're getting a steep rake, and it'd be some task to get that in and out in a pre-season. A lower platform, with one end of the stadium open and accessible would seem to be easier even than Hampden to convert (which took months).
I'm not sure if I'm onto something or not here....I'm sure others will find holes...it makes sense in my head anyway.