How about if boolean function would accept error clusters, we could simply use the compound arithmetic node (mode="or") to merge errors. Then we should be able to do an output configuration where we can select between boolean output and error cluster output. The output would be the boolean OR of all error conditions and the rest of the outputs in the error cluster would be the first error if we select error output.
I agree with altenbach, I like the idea of the compound arithmetic node allowing error cluster inputs. That would help clean up the error handling quite a bit.