Yes, I definitely get the impression from Fowler that, while he knows the correct high-status English usage and can explain how it came about and how to use, he also knows that it's a little silly.

All the same, I do find ‘shall’ useful. As long as I remember not to use it when Fowler would use it as a simple future marker (‘will’ is the only simple future marker in my American dialect), I can use it to express determination. If people think that ‘shall’ and ‘will’ are interchangeable, then I can't do that; but as long as people know that ‘shall’ is something funny, then at least they can look up what I mean if they don't know.

It would be much nicer if things worked the way that simplicio said. Once the last first-person-simple-future user of ‘shall’ dies, then it will be safe to implement this rule. (So please hold off on the Singularity until then.)