It would be fantastic to see a button that could restore all of your lost troops after battle and have them evenly distributed over each of your barracks. It saves having to go and rebuild your army manually.
I anticipate the idea behind not having such a button is to prompt the player to consider replacing lost troops with a combination that is different, in whole or in part, to what it was most recently. That said, your post got to me thinking how such a function could be applied. I think a dialog box prompting a player to replace lost troops -- with an option to have the game do so automatically to its most recent composition -- would be of benefit. For players like myself, the ability to check a box to disable such future prompts and instead be able to access such an ability through an on-screen menu would be welcomed further.