JL5K: Villains?

I've been knocking around trying to come up with the bad guys for my Justice League 5000 to fight. Here are the possibilities so far, both my own and from the folks who have participated in this thread over at RPG.net.

• A team-up of the greatest villains of all time, composed of time-travellers and immortals.
• Solaris the Sun-Eater
• Per Degaton and henchmen plucked from various eras.
• The Crime Syndicate (the evil anti-matter versions of Superman, Wonderwoman, and Batman)

The current discussion on the RPG.net thread about Psycho-pirate remembering the pre-Crisis world has me thinking. Could the plot involve using Psycho-pirate's brain to reconstruct the pre-Crisis multiverse?