You can certainly find such journals if you are not too career-minded. Although there are not many examples in recent issues, Rendiconti Torino has open access and a tradition of publishing occasional expository articles, though typically less than 30 pages. It will effectively referee such papers provided that they appear to have a novel approach (as is the case of yours) thta cannot be found elsewhere. Publishing in such a journal may be more satisfying than simply leaving a paper on a homepage or the arXiv (which you can still do anyway). [I am its director, but it's a non-profit concern and I feel that such publicity is in the community's interest.]

You can certainly find such journals if you are not too career-minded. Although there are not many examples in recent issues, Rendiconti Torino has open access and a tradition of publishing occasional expository articles, though typically less than 30 pages. It will effectively referee such papers provided that they appear to have a novel approach (as is the case of yours) thta cannot be found elsewhere. Publishing in such a journal may be more satisfying than simply leaving a paper on a homepage or the arXiv (which you can still do anyway).