Thanks EGOL, Kevin and Alan - that last mention from EGOL is along the lines of what I am worried could happen because of the motivations behind the posts, which is to cite each other.
Their authority on the subjects where they intersect is legitimate - but these articles would be generated because of those intersections. If I didn't have a blue widget client then the red widget client would have little impetus to write a blog post that extols blue widgets. Even though there's nothing in the posts that isn't true and all clients are qualified authorities to be cited as described. It's just that the posts would be written because the SEO guy (me) sat down and said "how can these clients cite each other legitimately?" rather than red widget guy writing an article on blue widgets and then being lucky enough to have someone (me) who can put them in touch with a blue widget company to cite and be cited by.
They're all on different IP's so that should be okay.
I think I'm going to go ahead with this but I'll tread lightly as recommended. Thanks again, thumbs up for all!