> Reading default config from connections will not work reliable. Because the widgets like WPushbutton behaves by default different if you connect Left, Right or No-button connection

That's not true -- as you've changed it the set methods do different things based on the existence of other connections. That will appear as strange action-at-a-distance to a skinner.

A WPushButton calls setControlParameterLeftDown. When will a connection get set?

Your System
* If it is a left from-widget connection. 
* If it is a no-button from-widget connection.. only if there are no left connections.

My system:
* If it is a left or no-button from-widget connection. 

A knob calls setControlParameterUp:

Your System:
* Only no-button from-widget connections. 

My System
* All from-widget connections

In your system, the skinner has to consider:
* What is the type of the connection.
* What other connections are there?
to know whether a connection will receive an event. 

Granted, it currently doesn't make sense to think about sliders because today they don't have left/right event specificity support. But they may in the future and they may get gesture support or modifier support.