Artboard Properties as Menu Commands
Add "Maintain Width and Height Proportions" to Menu Commands so that it can be assigned a shortcut. Other artboard features like "Move artwork with Artboard" and "Scale artwork with Artboard" would also benefit from this, I lose a lot of time checking and unchecking these boxes.

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Nick, we need all of the options and functions Ai has to be available for assigning a hotkey, not only these you mentioned.
What about Constrain Width and Height Proportions? Or the Width / Height field in general?
There is a general request on the topic: Assignable keyboard shortcuts for EVERYTHING — http://illustrator.uservoice.com/forums/333657/suggestions/31609237 (and you upvoted in a half a year ago).
Do you prefer this one to stay as a separate request?