Given that the existence of a reference is fairly trivial to check, I'd wager the authors would not care enough to pay for this. As for 'fit', this is very much in the eye of the beholder and a paper can be cited for the most trivial part. Overcitation is usually not seen as a problem. Omitting citations the reviewer considers 'essential', often from their own lab or circles, is seen as non-negotiability.
So the better 'idea' would be to produce a CYA citation assistant that for a given paper adds all the remotely plausible references for all the known potential reviewers of a journal or conference. I honestly think this is not a hard problem, but doubt even that can be commercialized beyond Google Ads monetization.