I just want to say, that I now found some ways to get the right behaviour that I want, but its not complete yet. it looks like this:
Thanks again, for the people in the IRC channel #unrealengine on Freenode for their help and support.
I try to use classes for each screen vehicle, It works with the first vehicle , but fails for other ones, I see vehicleblueprint_child2 is NOT receiving input. I try to activate input like this but it fails.
Some quick feedback: pls DONT answer this question anymore! I will work on a full featured answer in the near future, and post my solution. I got it now finally working exactly how I wanted it. (with a player controller, and all the fancy stuff) Thanks again for all your support (especially from IRC !)