I think WotC (and other publishers, such as Goodman) have missed that part of the reason T1 and B2 were the starters for zillions of campaigns was not just their level nor their availability but because they formed a solid base for a campaign: There was a full town (and more, in the case of B2), offering every service a new adventurer might need, along with the chance for them to interact with those on their social level, a plethora of low level hooks, a chance to serve a higher level power and multiple nearby adventuring opportunities.
I like "The Sunless Citadel," but the tentative way base towns were placed into the Adventure Path was silly -- we don't really need the stats by themselves. Either go ahead and give us four pages (at minimum) on the village, or place the village off the edge of the map and just say to use one of your own. But for a module that was meant to be the jumping off place for new campaigns, it was a mistake, IMO, not to provide that base. The starting village -- can anyone even remember its name? -- should have had a fleshed out local leader, an inn with a large scale map, a smith, a multi-faith temple complete with a cleric capable of training party members, a grizzled old veteran (either the local political power, the smith, the captain of the guard, or a guy perennially in the corner of the tavern) who can train melee types, and a kindly old wizard capable of casting Identify and training new wizards. Toss in a minor local threat (since Sunless has kobolds and goblins, make it something different, like a local bandit chieftain) or two, and you're good to go.
Hell, I once ran a campaign for months that never got past the starting village, between local threats and adventures spinning out of NPC character hooks. Any new Adventure Path from WotC needs to do the same. Make subsequent modules take people all over, but if you're doing site-based adventures, provide the solid foundation to have them all begin at (if the DM and group so desire).