Let's start by saying I'm still on FM11 so no idea on what you guys did to this on FM12 but I doubt you included it.
My idea is... *drumroll* divide the national pool into sub-categories
What's the point of having a list of roughly 100 players where over half of them are only relevant for the U21/U19 squads? It's a total nightmare to browse it. All I want is the ability to set my group of core players which I'd call up no matter what, whenever they're available. Then I'd have a secondary list of primary backups/squad players, a bigger list of afterthoughts for whenever there's an emergency of player shortage, and special lists for youth squads.
It'd make life so much, much easier as an international manager. Currently what I do is go to the player search screen for every single position (there's always good players the previous manager forgot to put on the national pool, I don't want to miss them), and analyse the best available players, for every single call-up. It's incredibly dull. This way it'd be just a bunch of clicks:
1 - go to the core players list screen and click a "call all available players from this sub-list" button
2 - analyse the gaps in the squad and look at the 2nd (and eventually the 3rd) list of who fits them best
3 - look at a screen with the differences between the team you just picked, and your assman's suggestion of choices, and click confirm.
Then maintain the lists throughout the season much like you'd maintain the squad status of players - move them casually whenever you think they deserve it. Except these lists would be private and not affect the morale of players.
Surely it's far simpler and easier this way?