For picture style controls it's true, not all cameras let you preview adjustments in realtime. 5D2 and 60D do, so those users may find picture style controls redundant.
I use ML preview a lot instead of standard canon menu. So i'll suggest to keep them in advanced menu, maybe only on selected cameras?.
Also Mirror lockup with self timer, for me it will be default.
I have DOF sticky set to ON and Clear Overlays set to DOF, and I use it as a switch when sometime I want to keep LV clean, faster than opening ML-menu

One thing I've tried to do to clean up a little the menu is to move Power Menu and Config Menu to Tweaks Menu using a submenu like for shortcuts or LV zoom settings (but failed).
I've also re-enabled ALO/HTP on my test because was missing it

For me on 600D less used things are:
Defishing (having no fisheye lens...)
Vectorscope (didn't even know what it was before, but looks interesting to have)
Image Effects, not useful but why remove them, maybe we can be show only in simple menu mode?
Also to remove clutter IMO is to have all the "set once and then forget" options to a single menu organized in submenu:
MENU MOVIE (for example):
- BitRate
-- like now
- FPS Override
-- like now
- HDR video
-- like now
- Image Effects
-- like now but only in simple mode
- Settings (or movie tweaks?)
--Time indicator
-- Movie loggin
-- Movie restart
-- REC/STDB notify
-- Movie rec key
--Force Live view
-- shutter lock
MENU SETUP (instead of tweaks):
- LV Zoom Settings:
-- like now
-
Arrow Key Shortcuts:
-- like now
-- (600D) DigitalZoom shortcut option
- Play settings
-- all what is in menu Play now
- Power settings
-- all what is in menu Power now
- ML Config settings
-- all what is in manu Config now
- Debug (only visible in nightly build)
-- Screenshot
-- don't click me
-- stability test maybe one for one since already in a submenu here.
MENU SHOOT
flash options like flash/no flash and 3rd party flash can be moved to a submenu (maybe better remove flash-no flash and add 3rd party flash to set button instead of 180° to shortcuts in photo mode)
MENU DISPLAY
- display settings
-- contrast
-- saturation
-- Color scheme
-- Image position
- layout settings (with a better name)
-- Upside down mode
-- Orientation
-- Auto Mirror
-- Screen Layout
- Force HDMI_VGA
- Crop Factor display
- (600D) audio meters
Note: Upside down on my 600D works but I think that to be useful it need to reverse also arrows since probably camera will be upside down too.
FOCUS MENU
- Trap Focus
- Focus Patterns
- Follow Focus
-- like now and also with
-- Focus step size
-- Focus step delay
-- Wait flag
-- Focus end point
- Rack Focus (with a submenu like stack focus)
-- Rack delay
-- like now
- Stack focus- Focus box (LV) from display
MENU HELP
like now but with also
- shutter count, memory and temp display
Other small suggested change is Menu order:
AUDIO EXPO MOVIE SHOOT FOCUS LIVEV SETUP DEBUG HELP
cause livev can be "set and forget" if used with display presets (I have all active on 4 different presets)