Yeah, I've been still trying around and now I'm pretty sure this is where you set the type, and I'm also now assuming there's no way to carry both signals and control data in the same input as it is. This seems to require changes to the core of Pd elsewhere, right?
???
i don't think so ...
[writesf~], [tabwrite~], [snapshot~] etc.
all of them vanilla objects, all take signal AND message inputs
best
oliver