My go to key for pause menu is usually the escape key. If it doesn't intrude on the gameplay, can I have the escape key to pause the game? As well as maybe mouse buttons for the main menu? 

I am just going to make P for Pause and while in editor I have UI buttons to use the mouse.  But I am going to make the UI navigational for users be able to use the limitation Keys to navigate as well.  so basically (A) = up, (X) = down, (Space) = Submit.  or something like that.  Just so that way I'm only using those keys.  I read earlier that there are no exceptions.  But you can also code in (if(inEditor){do what ever you want} then when you go to play it on web or on client it wont' run those lines of code.