I work commercial... even so...
1) Too wet.
2) That's one weird bathroom layout. I wouldn't dream of it since no fireman would ever think to look there when time is critical.
3) Too wet.
More generally, a SERVICE disconnecting means is a critical piece of safety gear and is not to be shoe-horned in to a home.
This is the last item one should think about scrimping on.
Out my way, most SERVICE disconnects will be outside: NEMA3R, even in snow country. When needed, a 'bird house' is set. (micro-roof)
If I were to run into cramped quarters... I'd put the disco outside. It'd usually be quicker, too.
As for the history of various Code provisions... I don't have the interest or the time.