Maybe he should investigate the 'hooks' Apple provides to it (and several other "Core Services")? I know I have at least on Finder type, third-party app that uses the Quick Look technology.
But I can understand his frustrations, every time someone comes up with a really good, new idea, there is a chance that some OS maker will either try to buy it or duplicate it.
I think you said you and once used "Greg's Browser" back in OS 8 and it used the 'hooks' in StuffIt files to show exactly what was in them. Not sure anything is able to do that, even now.