> ... i wonder if it could be codified.

My point was "less features" would be probably an option. When I first saw the sheer number of tabs I was like wtf.
grandma can probably safely touch any of the different corners of the screen, this leaves 3 features/options and back/cancel button.
when focus is in a functional screen, we still have only 3 corners (see back/cancel button should remain where it is) to work with.
maybe 5 elements if we assume grandma can safely touch/distinguish 6 elements on the screen.
like choose face (whom to send teh money), maybe change type of tx (bitcoin, silver IOU, other ...) and type/choose amount.
(if gui has 6 elements, then also "take/consult notes" & "wealth overview") ...

I like multibit's take on this, 3 fixed tabs in the app and all others can be closed (if you open them).
thus you can have the client as complex as you wish (read open tab for everything) or boil it down to basic 3.
what is "all that grandma needs"?
- make 'em feel my generosity - send stuff
- who is in my address book (view/add/probably should not edit - could corrupt vital tx IDs)
- what's in here (list of assets - what can I spend / liabilities - p.ex. memos about bills due this month, year ...)
- add/remove stuff to/from screen (show/hide options/features)
- cancel/back/home
- tutorial / help / training mode (I'd like to allow user to play with the app without consequences, demo mode, maybe change the background, show in the banner if this is the real or training session, let her explore the new mighty wallet)

yes, few big buttons