Two conflicting reports on a Combinatorics paper
I'm not sure you can get a definitive answer here, but my suggestion would be to let the paper stand on its own and just submit it to a different journal without further comment.
I don't see anything wrong with making a suggestion to an editor, but suspect that it is likely to be rejected. If you give them full context then I think it is even more likely to be rejected.
Of course, a new journal might happen to use the same referees as the pool of experts in a small domain may be limited.
But, in general, let the paper speak for itself. It may be that the negative reviewer is the one with a more complete context in which to judge whether your paper is interesting (enough) or not.
And, yes, this is just an opinion and a personal view.