Unsealed spellbook should allow you to swap summoners around for free
I'm sure I'm not alone when I'm saying that I like to keep my summoners on certain keys, like heal on D and flash on F or if I use TP, flash on D and TP on F. Now the problem I have with unsealed spellbook is that when I start my game with heal/ignite on D, flash on F and then I want to swap whatever is on my D key to TP, it leaves me with an unfamiliar summoner order until I swap back and we all know what happens when we have summoners on the wrong keys.
Now my solution is pretty simple, when you click on the summoner you already have, it will swap around just like in champ select with no cost. It might also need something to show that you just swap the summs, not that you get a copy of the summoner.
EDIT: Velzard of Koz had the cool idea of being able to swap the two summoner around even without the rune, it will probably need a modified UI from unsealed for just the 2 (or maybe just a button), but it would solve the unfortunate cases where we go in a match with the summs on the wrong key.
Also as some of you pointed out, a work around for now would be rebinding the 2 summoners around.