There are 2 good examples of MVC applications using Alloy that are available to you.
This one is great because you can download the actual app for IOS and Android to follow along with. If I remember correctly it is using custom tabs. https://github.com/appcelerator/Codestrong
The other, which is closer to what you were looking for is Field-Service-App. This example doesn't use tabs, but does have a nav bar that controls the app at the top and switches between list and detail screens. https://github.com/appcelerator/Field-Service-App
These examples will show you methods of separating the logic from the presentation just like you are asking for. They will also show you custom font and if you get into it enough, the Field-Service-App works with Appcelerator's cloud solution if setup properly.