Super bizarre, probably worded improperly (is there even a precedent?), and probably more fit for an un-set than a real set. Still, I can't not put down wonky card ideas when I have them.

Yeah, I think this would be un for purely practical considerations -- but I think it may actually work under the rules (modulo a few tweaks). Although wizards might template it as having a second library which you can swap in at any time (which would be less elegant and less interesting, but possibly more reliable)

It probably needs to be to choose a library on a per-spell basis, else "search your library for a card. Then shuffle your library" becomes "arrange your library however you like" which is a cool interaction but probably a bit much.

Previous text:
"Split your library in half, rounding one half up and the other down. For the rest of the game, you have two libraries. If you would draw cards, you choose which library to draw from. If a spell or ability instructs you to interact with your library, you choose which library you interact with. (Interacting includes shuffling, searching, or moving cards from your library to another zone.)"