I have considered a similar plan, really just an alternate take on your suggestion, which is creating a new profile and transferring ownership of my own (semi) popular projects to it. The problem is, I then give up my 2+ year old Github account for a brand new one. And then I also give up proof of other external projects I've contributed to, including some big name open source projects.
Github really should let users have control over what repos are shown in their profile. I mean, fine if employers want to use Github as a resume, but at least we should have control over which ones of our projects Github displays, then.
But the most important is that you don't think those contributions will be seen as a negative, good (anecdotal) data point. I'm beginning to think that I may be worried for no good reason.
Thanks for taking the time to comment.
Anyway, a technically savvy interviewer would still be able to find your commits but your personal profile will be cleaner.
Edit: I don't think your contributions will be negative but it is your GitHub, your rules.