They can uncover plots and deeper bigger evils but none of this ambiguous wishy washy gray area bullshit. New group is drawn together to do quests for a certain area, earning coin killing monsters. They established themselves as something similar to the slayer's take and do missions all over the continent. It's not huge threat that it would attract the biggest hitters, but it's enough of a threat that the PCs are powerful enough to deal with it. The overarching threat is a Tharizdun/Bhaal cult who's looking to overthrow the city. Anyway they have some opportunities to explore but also some clear goals. SO in this scenario, the party is say entry level members of the Slayer's Take or perhaps they're part of a new task force created by the Theocratic government to hand specific tasks.
This lets you basically set up your campaign to take place over around a year, so every year or so you have new Merch, new fanart engagement, more chances for your PCs to playtest subclasses for potential new books, etc. ANd by telling the players more or less the goals of the campaign and giving them a sandbox instead of long term improv. If it's anything like Sword Coast cities like Waterdeep and Baldur's Gate you could easily run a 1-5 campaign in that city. Vasselheim is supposedly this massive rich history city, and we've barely scratched the surface of it.
Here's my pitch, Campaign 4 runs around 50 episodes.
