While I haven't heard of any such service, even if one existed, the core issue would be the same... they would likely advise you based on opinions and arguments that they've read.
If such a service did exist, I'd think the things they would look at for the founders are:
Most of the factors would be subjective, just like doing this yourself would be.
I would say the best people to advise you on this would not be a consultancy, but other entrepreneurs based on their own experience with their own equity structures.
Along the lines of what Chrissie said, you could find an entrepreneur / influencer in your niche and have them do it for you. You could offer to get them onboard as an advisor with a 0.5% to 1% stake in the company and kill two birds with one stone.
What you are talking about is a dynamic equity split approach that attempts to value individual contribution. Mike Moyers grunt fund would be a good place to start - review his "slicing pie" book and if his idea resonates with you, reach out to him to get a recommendation for a grunt friendly lawyer.