It's settled then ;)

Not clear what is necessary to implement and how it is different from what is already available.

Alt+BkSp is generally reserved as a doppelganger of Ctrl+Z. As soon as Undo is implemented, Alt+BkSp will be used for undo, as well as Ctrl+Z of course.

Definitely not in 1.6, probably the earliest version this could be fixed is 1.7. Time-wise this should be in May or June. But still, it needs to get some more votes first, otherwise it might be postponed till 1.8 or later.

Thanks for the idea, Chris!
Seems to be also a nice general solution to this request:
http://roadmap.cintanotes.com/topic/4753-always-on-top-for-notes/