Is there anything like an ARexx port on software used in Unix and Windows such that one can easily command other software esp closed source ones to do things. And thus open up for integration and batch processing?
Seems to be the missing feature, or did I miss something?
Not really. There are tons of messaging libraries and RPC solution etc., and there's even an open source REXX port (Regina, used in AROS) but next to no software *uses* them.