For SS28 the two things that come to my mind is the relocation of studio tour plaza just like you had said it.Food for thought, have you considered how interactive Mario Kart is probably going to be?
Hell, @Teebin mentioned in the past that the interactivity levels for the ride beats MiB by a landslide, and that I am more willing to welcome an IP that is classic by it's own right, and not a broken franchise.
As for SLoP, it'll do fine. I would doubt however that attraction taking that much space at this point.
As for SS28, I am curious to see what that turns out in the end. At this point, I am thinking and almost betting that it will be involved in the creation of the relocated Studio Tour plaza.
2nd thing on my mind I hate to say this but Fallon which I'm hoping it never happens.