Why not one of the flasher wrasse family. Or even a solon fairy wrasse.
Dwarf angels are hit or miss, the flame I had was a miss. He nipped my firefish and my powder brown tang smashed the flame into the tank glass. The flame was back at the store the next day. Other folks have had great luck with them, me not so much.
Depending on how large you go with tank size(a 6 footer at least cough cough) a couple more fish temporarally would be fine. If you were going to upgrade soon(a year or so) why not keep the tang? If no plans to get bigger then I do applaud you.
Now on to the tank size tif. FTMMWS was right about that. He may hang around like he's medically mellowed but there are also internal stresses(organs outgrowing the body) from not much roaming room(that's what I have heard anyway.) Now the argument didn't need to happen but nontheless, he made his point and I do agree with him, but since you are going to sell the angel, no biggie in my opinion. However, the longer tank will allow the koran to develop adult colors and fetch a larger chunk of money.