Leadsled is matters not one wit whether the mistake is made by the RPT pilot or the GA pilot. Humans make mistakes hence we design systems that mitigate those mistakes, ergo, controlled airspace.
If two aircraft come together in controlled airspace there has been serious, most probably serial/multiple, human failings but its not a system design fault.
You're touting a system that can produce aluminium rain without human error. The GA pilot may have assiduously turned the transponder to mode C and in good faith believe its working properly - that doesn't mean it is.