Since I am not getting any further with my current song at the moment, I have started to familiarize myself more deeply with Reaktor and not only construct my own synthesizer but also my own effect plugins. That was easier than I thought and was done in just a few days.
For the nerds among you: The echoes of this effect do not decrease linearly in volume but exponentially, and it is possible to make the echoes more muffled after each repetition - in contrast to normal echo plugins where the muffledness of the echoes can only be set the same value. The effect is only very subtle and will certainly not be noticed by anyone here on the next album.