I wouldn't add an Arabian Pseudo...those guys get real nasty over time. Unless, you have a pretty good size tank, then my guess is that he's going to harrass your Royal Gramma.
As far as the Flame Hawk is concerned, I had Flame Hawk's in my systems for years and years and I have never seen any one of them bother the cleaner or fire shrimps. Currently, I have a pair of Flames and both shrimps in a 135 gallon tank with for over a year now with no problems.