While all of these ideas make sense logically from the perspective of improving the team right now, unfortunately I doubt any of these are options the FO seriously considers, especially when it comes to Barger. If the only reps he's getting would be on rest days to guys like Chapman, Springer and Vlad, it wouldn't be enough for one of the top prospects in the org. They're going to call him up when there's an everyday spot for him.
In Clement's case I agree, I've been wanting him to hold a spot on this roster for a while now too with his hitting vs LHP, but if the FO really believed Clement was a capable enough SS defensively to back up Bo (we already know he's a capable 3B defensively), then he would have taken Espinal's roster spot a while ago.
Plus, with the way they're apparently going to be easing Bo in once he's activated, I wouldn't be surprised if he wasn't completely 100% right now but they desperately need his bat back. I doubt they DFA the SS that they traded for because they don't trust anyone else there defensively if Bo's hurt, and risk being back in the same situation if Bo gets hurt again.