I recently had to rehome my male Red devil because my smaller male Green Terror was mauling him, I may have to rehome my oscar for the same reasons, he's 2 inches bigger then the GT but he was nearly killed the other day by him, so He's in a hospital tank healing now before I decide what to do with him.
If your Midas owns the tank then make sure any cichlid you introduce is smaller then he is and not of simular colouration. otherwise the Midas may take offence to the new cichlids presence. A pike cichlid may be the easiest to introduce.
In all honesty though a smaller GT or Pike cichlid may be best if you must have a cichlid.
Personally I recommend A Birchir of some sort, A fire eel , A large species of pleco or Synodontus maybe. Trust me though You can't go wrong with a nice Ornate Birchir.