Sith assassin would benefit any of those teams with the TM boost, but most obviously pairs with Revan (to maintain pure Sith empire team and the resultant+50%CD) or Maul (for pure stealth synergy)
Personally, since Vader already acts as a TM engine for Palpatine,
And, you likely have your fastest mods on darth revan team,
I would go Sith Marauder with Revan (maintains pure Sith Empire, and he is another brutal attacker to keep the damage flowing while trooper tanks)
Sith assassin with zMaul for a speed boost for that team.
Palpatine squad though, gains equally from Sith and Empire tags (double dipping on Palp and Vader) you can actually throw in empire teams/toons just as easily, ideally some control or rebuffing elements to play on The zeta lead. Sion And Nihilus Will do okay in that squad, but you can as easily throw in shore trooper, tarkin, Tie fighter pilot, royal guard, or Thrawn into the lineup...
If you go that route, you could drop your nihilus into any of the slots in your maul squad (eventually you will probably want to pull dooku into a separatist squad down the line, so he or assassin would be my first choice - if I recall from your other thread, you already have a pretty boss Zavage, right?
Not sure if I am helping or just rambling...