My ideas about possible screens.

* Generate new address
receive "generate new address" command from USB
display "Generate address?" "OK/Cancel"
generate new and

display "Show priv key?" "OK/Skip"
display "Priv key" "" "OK/Cancel"
display "Address" "

" "Store/Cancel"
store and

transmit

to USB

* Sign transaction
receive "sign transaction" command and from USB
display "Sign transaction?" "OK/Cancel"
parse values , , , []
display "Send-to addr" "" "OK/Cancel"
display "Amount" "" "OK/Cancel"
display "Fee" "" "Sign/Cancel"
sign using stored private keys for [] into (what if some send-from addresses are not in the wallet?)
transmit to USB

* List addresses
receive "list addresses" command from USB
display "List addresses?" "List/Cancel"
loop through

[]
transmit

to USB
display "Address" "

" "Next/Cancel"
end loop

* Delete address
receive "delete address" command and

from USB
display "Delete address?" "OK/Cancel"
display "Address" "

" "Delete/Cancel"
delete

and its from storage

Maybe there could be also a PIN security feature for the device. The PIN would be a hexadecimal number entered in a binary form.
Once the PIN is set, the device auto-locks when disconnected or after some period of inactivity, and then it needs to be unlocked next time.

* Set PIN
receive "set pin" command from USB
display "Set PIN?" "OK/Cancel"
display "1111 0111 10*_ ___" "F 7 8 _" "0/1" (enter 16 binary digits)
display "Setting PIN" "" "Confirm/Cancel"
store

* Unlock device
receive any command from USB when the device is locked
display "Unlock device?" "OK/Cancel"
display "1111 0111 10*_ ___" "F 7 8 _" "0/1" (enter 16 binary digits)
display "Unlocking device" "" "Confirm/Cancel"
verify
unlock device and continue