The answer is maybe.
Ornates get considerably larger than the other polys mentioned by yourself or others.
In a 125 gallon tank you can have a variety of smaller polys living safely together.
I have to agree with the others who said don't do it. I have an ornate and a variety of other smaller polys. I moved out my ornate when she hit 12" and was starting to get large enough to eat the other polys. I've seen her eat chubs that were 7-8" in length. They are fish that are similar in overall body shape to polys, and swim considerably faster. They were eaten with no problems whatsover.
I'm not saying she would eat her poly cousins, but I wouldn't put it past her to do so either. Play it safe and get some delhezis or more senegals.