I am okay with players designating other players if they are going to be away and do so beforehand. It doesn't make a lot of sense in context, but I wouldn't want real life to force battles to be auto-resolved.

would also be fine with fighting the battle myself but I can see that some players would worry about my being biased since I am controlling other factions. I can promise you that my goal isn't to "win," so I would fight the battle for you to the best of my ability, but I don't feel comfortable forcing people to let me play the battle unless they miss the 24 hour deadline without letting me know they would be unavailable beforehand.

Also, just so everyone is aware, battles without a character general in them (ie, captain led battles) will be auto-resolved.