It might get a little laggy with a ton of people in close proximity defeating GMs. My suggestion is have the GM invasion as either a regular invasion event like the Rikti and Zombie invasions or have it occur for every CoH and CoV anniversary.
The first step in being sane is to admit that you are insane.
One nice thing they can easily do with Pocket D is adjust the threshold of how many characters are allowed in before creating a new instance. That makes them better able to control lag compared to an outdoor zone like Atlas. An outdoor zone can be well under its max character threshold yet still have enough players clumped up to trigger slideshow-mode. So I'd say if lag is a concern, that's all the more reason to have it in Pocket D instead of in normal zones. It also lets people more easily ignore it if they don't want to participate.
Freedom: Blazing Larb, Fiery Fulcrum, Sardan Reborn, Arctic-Frenzy, Wasabi Sam, Mr Smashtastic.
I logged on to Test yesterday for the anniversary event and it was amazing. Pocket D was full of AVs, many of which I've never seen in game. It was so much fun, even when a particularly powerful bunch of them would mass-kill a bunch of players.
I'd love for that to become a rare event (perhaps an anniversary-only event that lasts 2 days), where DJ Zero puts the call out for help because there's a dimensional rift and super-powered entities are pouring into Pocket D. As with many events, there should be badges associated, maybe for participating in 1, 5, and 10 kills.
Freedom: Blazing Larb, Fiery Fulcrum, Sardan Reborn, Arctic-Frenzy, Wasabi Sam, Mr Smashtastic.