Get a Line6 M9. It can do all the things a Fission can do and more. And it's way more tweakable and has tons of expression parameters. I've used it for Octave up, 2 Octaves up, 5th up, 12th up, 4th down, and combinations of all of these. You also aren't limited to just these intervals. Just stack the pitch glide effects and put some dirt after them.