So, DS Bastila and Canderous seem like the obvious choices. I wasn't surprised at all to get those two, but I'm pretty stumped on what else will be needed.
I just played through the end of KoTOR, and you can make Zaalbar come with you for the DS ending if you choose the right dialogue, but he doesn't actually change alignment, so I don't see how they add a DS Zaalbar as a character.
The other two companions at the end of the DS playthrough are the droids that we already have.
They either need to do some lore backflips to scrounge up 3 more new DS companions for Darth Revan or Sith Bastila and Canderous are the only new toons that could be required for a Darth Revan event in order for it to be the same construct as the event for jedi Revan.
Possible options for the remaining 3 toons required would be JKR himself as part of a "villains fall" type of construct, the droids (T3 and HK) because they follow no matter what, or Carth and Juhani as new marquee companions for the early stages of the event before you turn on them (we still haven't seen Manaan or Kashyyk battles and they could be used there).
There is really no sensible way to add 3 more DS companions, mirroring the way LS Revan was introduced. They almost have to incorporate something we already have, and I really don't see it being KoTOR II toons or generic SWTOR sith. Either way, any old republic era toons are going to be needed for something so I'm starring and gearing anything potwntially relevant.
