This is interesting, @Katrin_Kellner, thank you for sharing. This type of simulink-ish programming ability was one of the use-cases that drove the development of the NoDL, to statically describe the interfaces of individual nodes so they can be “connected” at design-time instead of only at run-time. Is that something you might find useful here, or are you going about that differently?
Anyway, that functionality exists (and is under active development) in Foxy and Rolling in case you’d like to chat. Right now we’re primarily using it for security purposes, but we’d love to have another solid use-case, particularly one that we always hoped would happen 
.