Thanks to MomoTheNinja for indulging my theoretical exercise, I appreciate it!
However I am very intrigued by Sentia's idea of using Darth Maul and I think I might try that for now. Especially as I have an old school Sith squad that has recently lost it's Trooper thanks to Darth Revan nicking it; if I take out one other of the remaining four, I can put the other three in the Darth Maul / Enfys Nest squad.
All that remains now, is to figure out which three to use.
So Darth Maul (who is the only one I will need to farm / gear up a bit), Enfys Nest and then any three of Emperor Palpatine, Darth Vader, Darth Nihilus and Darth Scion. All of whom are g12 and fully Zetad. Each have advantages for inclusion. (No, I don't have Traya at a usable level.)
So one last question ...
Which three would you use?