I never would've guessed that adjusting the bone scale might do the trick! That certainly solves my problem (big thanks!), so the only issue I still have is that this solution is a bit unintuitive for someone to discover on their own. The setting's dialog does say that it adjusts the size of the bones and background, which hints at the max zoom being involved, but I wonder if there's any adjustment to that phrasing which could make that function more explicit. Maybe as simple as adding a second sentence like "Max zoom adjusts for new scale."
I do feel it would still be nice if the Zoom To Fit button were able to temporarily force a greater zoom level in situations where it runs up against the current joint scale's max zoom while trying to fit everything on screen. Mainly so the button can live up to its name of zooming to fit. Since it would only be a temporary change, any attempt to change the active zoom afterwards could behave the same way that it currently does if you increase the bone scale, zoom all the way out, decrease the bone scale, and adjust the zoom. In that situation, it currently just interpolates the zoom down to the new maximum bounds as soon as you try to adjust it, which seems acceptable in a situation where someone's just seeking a temporary 'big picture' view by using Zoom To Fit for its stated function.
Barring any of those changes being feasible, at least being able to search for this thread will help people in the future. Thanks again! 🙂