I'm not sure I understand your question or your post at all.

I think you have 2 procedures, each of them returning a result.

You want a result that unions the result of the two procedures.

You don't want to change the two procedures or even reuse their code as they are quite complex.

My suggestion:

Create a new procedure. There you call procedure A and store the result in a temporary table. Do the same calling procedure B.

Merge the two temp tables as needed and select them to return the data.