@Omar_Moretti: It sounded to me like what you want is an account overview screen. In my opinion, calling it a “non-unified Inbox” only leads to confusion. It’s not an Inbox because it doesn’t show a list of messages. It’s not “non-unified” because that implies the list belongs to only one account.
Note: Even when using the Unified Inbox the individual Inbox folders are still available. The Unified Inbox can also be disabled under Settings > General settings > Display > Show Unified Inbox.
I have no plans to bring an account overview screen back. The closest you can get is the account selection screen in the drawer (open the drawer, tap the downward pointing triangle in the colored header section).