I looked at the feature requests lists and didn't see one exactly stating this. Feel free to point me to an earlier one if one exists and I just missed it.
"Menu"/hamburger/whatever it ends up being pulls up only a half-dozen-ish options when in use.
I'd like to see the menu option ALSO pulling up the site-specific sidebar menu, if it has been customized. This would allow relatively easy navigation within the mobile interface between pages and/or sections of a wiki site.