If you're asking about GC outputting a requester chest blueprint (with the chest set to request all the required items), then no, it can't do that. The closest thing would be using the signal output feature, which you seem to have tried already.
It would be possible to create a requester chest blueprint instead, though I dislike how inflexible this is, since the single requester chest would likely not be able to accommodate all requested items if the blueprint is anything but small. It would also be inconvenient to use if one is playing with a mod like AAI containers with multiple different requester chest types.
When you get the combinators in your cursor—they're most certainly not going to be dynamic, since it's just a standard blueprint containing constant combinators. The combinators that get placed are not special and my mod isn't aware of them in any way, for it to be able to adjust their signals later on.
I could consider adding support for dynamically setting combinator signals based on ghost counts (for a selected set of ghosts) if I can think of a compelling use case that is not already served by what's available.
