After a long search, I have sometime then found the solution to the problem, the outside light switch of Arnold Electrical Engineering.
+ The outdoor light switch is easy to install (at three-wire lines), the accompanying documentation helps here.
+ The product is available in numerous variants, so that everything fits to the existing product line.
+ The build quality is absolutely dibasic.
+ The idea is thought through and solves the above problem in a meaningful way (continuous light, "normal" function with motion detectors, timer).
+ The service that the company provides electrical Arnold is also exceptional and more than helpful.
Despite the - at first glance - proud price, a product that I recommend without hesitation and gladly. Clear 5-star!