I don't want to sound like I am nagging you, but I will request this one more time. Please say yes or no and I'll stop bothering you.
On the Edit Titlebar Buttons dialog, when the user selects a HotKey, it would look very polished if the TitleBar Button dropdown wold auto-select the default image for that hot key. This would be very user friendly. I not sure offhand if this would be an CBN_SELENDOK or CBN_EDITUPDATE notification message, or what, but it ought to be an easy to add the behavior.