Hmmm - I had the opposite experience re: JD/Oscar. I added a 1.5x sized O to a tank holding 1 JD - JD shredded the O.
At any rate, whatever you go with, make sure you have plenty of structure and some visual barriers so they can hide from each other as needed and get all of 'em small. Let them grow out together and all should be OK.
If something dies prematurely, you may (or may not) be able to replace it w/o totally upsetting the pecking order int he tank, so you may want to go w/ one or two extra fish to start then cull if needed later on.
I'd probably try one O, 2 GTs or Sevrums and a JD. If they're all tiny to start, good. If you can'te get tiny ones, try to at least be close w/ the JD being smallest, O or Sevs being largest...
Later on, I'd use giant danios now and then as "disposable dithers".