So after thinking about it a bit I made some decisions:.
- 1st Edition AD&D will remain as an option with Temple of Elemental Evil ready to go, but it's not the "Mega" campaign
- 2nd Edition AD&D will be on the bench with Greyhawk Ruins ready to go. Looking through it again (first time in probably 10 years) I am a lot more impressed with it than I was. More on that later.
- If someone wants to try one in 4th Edition, well, since I'm already running in the Realms then I will use Undermountain. Not doing a lot of planning on it right now but it is an option.
So the final solution is to place the Megadungeon in my Dragonport campaign, where we're already doing some Basic/Expert adventuring anyway. I had already outlined a location known to be where the King of the Stone Giants rules - Skullcrusher Mountain! Added partly as an in-joke due to the song that the apprentices and I love so much (especially in Rock Band) it now will take on a somewhat more important role. I have ideas for several levels and monster groups within and I will put out more about it in a different post. We may not touch it for some time but that means I'm not under any pressure to get that first part mapped out. I consider it my training effort so I'm going to go fairly slow.
One other good thing is that the brain cycles spent on it have led me to think that it's really would not be that hard to do for 4E either. I think the core of the megadungeon experience is exploring, fighting, and sneaking through hoping to not have to start fighting, and 4E can handle those just fine. A lot of the crazy stuff from the earliest days like gates to other planes and pocket universes would work just fine with 4E. Anyway, I'm getting ahead of myself as that's at best the second one down the road.
Now that I have a place and a system I can start getting the concrete parts down and actually think about running it. Time to dig out the graph paper.