You can manually hide/show an individual interface using Lua script.
Interfaces["example"].InterfaceVisible = true -- or false
If it's just a style thing, then you could also use the same interface & use conditions to determine which graphics should be shown. Or you could create the 2 interfaces under different classes & use condition query to determine which to show/hide.
P.S: the none scriptable bit you mentioned is probably due to it not storing the new data in the save game files.
what i need is to change the characters interface list to replace an interface with another. This should not affect other action parts or scripts because the new interface has the same interface class.
What purpose has the "set interface of a character" at all? I cant select a specific character or even "unset" an interface again...
EDIT: seems to work now XD
It seems to just set an interface for the (current) character. all other interfaces in the same InterfaceClass get automatically deselected. Can a VS dev confirm this?