I broke down and used Gems to speed along defeating Syndrome. Now it's the long wait for his tokens to drop to welcome him. Just a heads up... The Omnidroid City takes a whole section of land to build. It's HUGE.
For the quests to get to defeating Syndrome, you only need Mr. I at Level 3 max. I'm sure more side quests will pop up once you level up Mr. I, but he's good sitting at Level 3 (and able to drop armbands for Syndrome at that level!) right now.
I had to store The Magic Carpets of Aladdin for the time being, and since I'm behind in the main story line (still have three sections + it's a small world to open up in Fantasyland, currently collecting tokens to welcome Zurg/Fauna/Donald), land is still a bit scarce.
Honestly, I don't think I'll be able to level up Mr. I or Syndrome to level 10 before the event ends, just because of the long wait times on their items dropping. Hopefully the developers will see that many folks were twiddling their thumbs for days waiting for the new characters to welcome during the event, so that they could possibly speed up the content availability for future events...