Morning Rudiger!
I have come up with a feature request - hope I can explain it. You may have already thought of it, but just in case here it is:
You mention being able to assign multiple morphs to a single bone? Not sure how youmade this work but my idea is to seperate the number of actions equally around the 360 rotation (or 0-100% of proximity to the control bone)
e.g.
you have the following actions, with the added naming convension below
ShoulderUp:1:roboBoogy
elbowUp:2:roboBoogy
wristUp:3:roboBoogy
fingersUp:4:roboBoogy
now you could create a control bone for any of those, but if you create a bone called 'roboBoogy', it will be split into quarters with each quarter relating to 1,2,3,4 above (and in that order) so just rotating it does the classic breakdancing move (although it's probably not called 'the RoboBoogy' you get the idea)
additionally, you could add the following action;
ShouldDown:2:roboBoogy
so that as you enter segment 2, where before the shoulder would return to its starting position, this time you are specifying that it goes down (past its starting point).
This brings you closer to the 'one bone animation' target

the original thought was that you could assign all phenomes to a single bone, and then use it like a theramin with a static control bone like I showed in my 2nd vid. but you could assign a bunch of unrelated actions to a sequence - heck you could even assing an action to several sequence bones by naming it thus:
ShoulderDown:2:roboBoogy,1:shrug whe're 'Shrug' is it's own morphDial bone!
I don't know if this is possible, or makes any sense, or whether you've already tried it... but thought i'd throw it out there! Could be really useful and minimise control rig clutter...