I've been thinking about it a bit more, and I've come up with this model for the next campaign.
- The rules set for the beginning is Mentzer Basic and only Mentzer Basic. Once the characters get to level 4 I'll bring in bits from the RC.
- I'll start with B2: Keep on the Borderlands because it appears that none of my players are familiar with it, and though I have some problems with it it's kind of a rite of passage.
- I'm going to fill in the Cave of the Unknown with the free megadungeon from the Yaqqothl Grimoire. I'm still working on the second level -- I spilled coffee all over my map. You should see it on the blog once I get a cleaned up version.
- The keep itself is fed by a town that's fairly nearby. I'll develop it as necessary for the campaign.
- The land beyond the keep, i.e. the Borderlands, is a wild and untamed region. It terminates in the realms of Chaos which are just as off the map as the Realm of Man.
- The goal of the campaign is to explore the Borderlands and eventually set up your own baronies in it. This will not be easy.
- The "Evil Chaos" mentioned in B2 will get a more suitable name and have an active cult among the savages in the Borderlands.
- Everything else will be developed on an as needed basis.
I might work up a rough map of the rest of the borderlands and post it here in a bit. I'm not 100% sure this is what I'm going with, but it looks fun to me.