Here are the villains from my outline. We have a main badde (Mandalore) his twisted henchman (Rothven) and a treacherous partner-villain (Brett Thousand). Thoughs, comments, and suggestions are more than welcome.
WOYIC MANDALORE
The Battlelord of the Mandalorians leads his invasion fleet from his mighty flagship Hohrac. Gruff, violent, and is never seen outside of his blood-red armor (including skull-like helmet) which has shielding on the arms that deflect lightsabers. During the final battle ObiWan leads the Aqualonian Rangers onboard the Hohrac, and engages Mandalore in single combat. But the duel is just a distractin to allow the Rangers to scuttle the ship, destroying the Mandalorian chain of command and removing their greatest weapon. In the end, ObiWan and Mandalore crash to Alderaan in the scuttled front of the ship, but both crawl out of the wreckage alive.
ROTHVEN DAGUHN
Roth is a Mandalorian commander and placed in charge of hunting down Prince Bail. Toth is a beutiful young man, with perfectly styled curly hair, imaculate blue/gold armor, and a delicate and graceful (almost effiminate) nature. He's also a sadistic sociopath of such utter cruelty the rest of the warlike and brutal Mandalorians are uncomfortable with him. Anakin's first use of the force is during the climax, when he yanks the blaster out of Rothven's hand as Rothven threatens Lhasa "NotPadme" Arcadia.
BRETT THOUSAND
Notorious pirate Brett Thousand allied with the Mandalorians for money. Beared, heavyset, and with a robotic eye, Thousand has an undisguied contempt for the Mandalorians. His pirate fleet of aliens and cyborgs shore up the Mandalorian blockade on Alderaan, letting the Mandalorian Invasion Force focus on their strategic objectives. When the tide of battle turns as the Hohruc crashes, Thousand and his ships abandon the Mandalorians and retreat to hyperspace.
PALPATINE
The leader of the planet Had Abadon, Palpatine is an old man from an unimportant planet, but is the only member of the Republic willing to aid Alderaan in this conflict. After the pirates flee, early model TIE fighters from Had Abadon attack in the final battle, squeezing the Mandalorians between two fleets, forcing a surrender.
(For the Mandalorian names, I've been using the Native American Wiyot language. Very roughly Woyic=Wolf, Hohruc=Snake, Daguhn=Pain)
I have some notes on a Sith Assassin who kind of hangs on the edge of the plot, but no real solid ideas how to intergrate him into it at the moment.