You can form alliances in Dragon Commander, though I don't know if that includes other dragon knights.
Patriarch is still fine, and could presumably create more dragon knights if he were so inclined. He didn't help any of the dragon knights that were being hunted down, so I wouldn't hold my breath waiting for him to get actively involved. Talana was able to make your character a dragon knight, so with the battle tower and dragon stone, presumably your character could find a way to create more dragon knights. It is also likely many dragons and dragon knights fled from Rivellon when the slayers started becoming successful, so you might be able to track them down in some future game.
