^^^I'm pretty sure the designs are actually just concept designs from early in the show's production, not related to future episodes about time travel. Hence why they're called the 'beta' designs. Some fans speculate that they might be used for older versions of the characters but as far as I'm aware there's no actual evidence for that. If you have a source for where you heard about them being for a future episode I'd happily check it out.
^^Its the same artist, with the same concept, but they dont have any obvious follow on / relationship to each other besides it being Yukari up to the same trick some other day- So I dont think they need linking imo.
p.s Its a fun idea but not how it would work- You also see the gaps at the exit points- they'd be obvious to either side of her breasts with yurkari's arms coming out of them.