I had raised a request for the rig exchange to be divided into two sections: rigs and profiles. I think there's a place for both, since some users like to have stuff ready to go right away and others like to do their own tweaking.
The best I can tell you is to write reviews of the commercial profiles you've purchased. If you've regretted your purchase, communicating what turned you off is good feedback for the vendor and the community.
I find this is an area that needs more work on the forums. For example, there are more posts praising commercial profiles than complaining about them.
At the same time, one man's flavour is another man's poison. I think a lot of those threads would deteriorate into factions for and against those profiles. Tone is so subjective, that there's unlikely to ever be a common ground for all.
As far as trying before buying, I might be working on something.
That's news. Look forward to hearing some clips.