Have you considered writing a Math blog ? Or sending your original paper for 'invited post' to an existing math-blog writer with appropriate scope and audience. Math blogs don't have the permanence of a math journal. But I'm pretty sure they get more attention from students than Expository math journals.
Your question reminds me of one of my favorite math paper Fractions by L.R. Ford in Amer. Math. Monthly Vol. 45, No. 9 (Nov., 1938), pp. 586-601. The first sentence of the paper is particularly delightful when thinking of the far reaching consequences this paper had. Take Rademacher exact formula for the partition number for example...
