So far the only known hybrid I know of is between Acropora palmata and A. cervicornis. Both are endangered so good luck getting permits to keep them. A challenge you might find easier to work on is manipulating the light field to stimulate the different fluorescing proteins a coral may produce. (I understand some species can code for as many as a dozen.) Might be interesting to have a tank with just a single species of coral but lighted to see a whole spectrum of colors produced by that single species. A starting point would be the articles by Dana Riddle.