Actually he can.
Sign into iCloud using husband and wife's individual unique apple id.
But sign in iTunes store or App store or iBook store using a single apple id (be it husband's or wife's)... both iPhones can have the same media (ie, books, songs, videos, apps), but different iCloud account to manage different emails, find my iphone, iMessage, calendars, notes, reminders, etc...
Just have to remember to sign out and sign in using different ID.
iOS4.x.x does not support this, but iOS5 does.
I am using 3 different Apple IDs to access Apps, iTunes and iCloud respectively.