Well it is going to depend on size, and the type of filtration you have, and rock lay out.
If you have like a 30 or 40 gallon sump, and great big skimmer and lots of hidey holes it may work. The bicolor isnt really going to be to much. The Scopas and the Niger both get pretty big. If you dont mind getting a bigger tank and you have the filtration for them now it might be ok.
I have way to many fish in my tank. I have a blueface angel, a coral beauty, 2 chromis, a clown, a swalisi basslet, a mandirin goby, and a tailspot wrasse. However its a 75 with a 20 sump and Asm G-3 skimmer and tonga live rock. My nitrates are reading and staying at zero and my phos is undetecable with a salifert kit.
If I put a smaller skimmer and took away my sump, I believe every thing in the tank would die or at least be stressed to the max.
I hope this made some kind of sense, since I am very tired and need to go to sleep. LOL
Steve