There are 13 sets from Origins to M19 (3 are small expansions, so technically only 10 sets), yet only 5 are currently in the vault at any time. Rotating sets and elite packs show how much time is left until rotation but disappear when not in rotation.
How about if when a set is not in rotation just grey it out and show how much time until it is back instead of removing it completely?
Same for planeswalkers out of rotation.
This way it shows off how much content is potentially available for the game while clearly displaying when each item will be available. Just put all items on a timer and it will better build anticipation and planning for them as opposed to just it not being there.
I bet at some point everyone has been frustrated waiting for and not knowing when the set/planeswalker they want to get is going to be available again. It will eliminate the need for having to go an external website to see what PW is coming back next (and save the devs from having to constantly update that post), and will help in keeping all the needed info in-game.
Just organize current standard sets on top and legacy with a banner below. Really not that big of a deal to scroll through. How often are you in the vault? Is that a event mode?
Why not have a selection panel for the vault similar to the one for booster crafting. Instead of scrolling through the vault, you select what type of pack you want to purchase (regular or elite), then the set, then the cost of the pack.