In thinking about the UI we have made some interesting observations.

Firstly the "code" for an AT cannot be changed (otherwise you could never trust it and basically the main point of ATs is that can act as entities that require no trust beyond understanding their code) but it is possible that the UI could be improved (without changing any of the machine code of that AT).

How this is best handled is still something that requires some consideration but it does make sense that the UI might be able to be upgraded despite the fact that the AT machine code cannot be.