Again, my skill challenge structure blows this out of the water. I suggest you read it again, and, rather than insisting that you have the one way it works, consider how it might work in a different way and try, very hard, to imagine out that would work. Here's the rub of how a skill challenge works, in my game: I present a challenge to their goal, they tell me how they solve it, and dice are rolled. If a success, the PCs solve it how they say. If a failure, I add pain points. For example, in a skill challenge earlier in my game, two PCs were trying to gather information on one of the PC's nemesis. They had heard that the nemesis had been working in a certain area of the city and so went to find out. They first decided to approach a business in the area that they thought would be likely to supply the nemesis, and asked there. I presented an employee who might know something, but was being cagey. They used intimidation to force the issue and have the employee tell where the nemesis was. They succeeded, which meant that they got one step closer (a single success doesn't win, but moves you in the right direction) -- in this case being pointed at another business owner who had handled most of the work, this guy just handling some subcontract stuff. So, they went to track him down.
From my perspective, the initial business owner didn't exist in my notes or prep until they decided on this approach -- it made sense that one would exist, so one did. The second business owner certainly didn't exist until they tried it. And, in that attempt, the fact that he was huge and scary (Sigil) didn't happen until they failed the roll to find him, meaning that he was now dangerous. And, the fact that he actually turned out to have a huge heart and loved his neighborhood didn't happen until one of the PCs made a successful Intuition roll when trying to figure out what the scary business owner's Bond was. And, that he supplied food until just last week, when the nemesis packed up shop wasn't prepped until they made the third failure in this chain, resulting in a loss condition for the overall goal of finding the nemesis in the city. None of this was prepped, all of it occurred immediately in play, and it used 5e rules to the hilt, with just the addition of the overall skill challenge framework I like to use for complex tasks. This one, in play, example changed a good bit about what has happened in the campaign, because dealing with the nemesis was delayed for other considerations.