That is actually a good idea...
So you suggest for Paizo to bring out like a Adventure Path Carry Case™?
Specifically one that is suited for card sleeves of course. With the new Adventure Path coming out next year this could be very needed.
I will probably also start making new type of custom campaigns that combines elements of the different Adventure Paths. This could work well keeping all the current Custom Adventure campaign stuff then in the carry case and all the unused stuff in their proper original Adventure boxes.
But unfortunately the best solution is to get Broken Token separators and slots at the current moment for keeping everything in sleeves. I would have loved if all the cards could fit as is in the Adventure Path box and inside the Adventure boxes. I like it when we reset the game and every time we complete an adventure we open the box and expand the game.
But I do need sleeves, some of my cards are starting to show a bit of wear from the constant playing they have gone through. Especially if its a card that will always be part of someone's deck.