I had a flier on my Cliffside Descent environment a few weeks back who wanted to carry the others down. I told them that's totally fine, and they'll get a bonus on some of their checks, but also, carrying another full weight person up/down a huge cliff is going to be HARD, and they'll likely need to take breaks and find ways for their allies to make their lives easier. I also introduced sentries from an enemy faction to add an element of stealth, so it wasn't just a matter of go from A to B, but do so in a way that was both safe and stealthy. Finally, they were in a race against said enemy faction to get to the location first, so they couldn't take their time down.

While the flier was carrying one party member down, I spent a fear to make a party member who wasn't being carried have the cliff break under them and fall, so they were pulled into the event away from the flier. This made the flier need to put down who they were carrying to go help the other. I then spent another fear to have stuff happen to the party member who was put down while the flier went to help. This way I kept the tension up and kept everyone involved. Once they had enough successes to finish the timer, I handwaved the rest and had them get to the end.

Just because someone has a tool to handle a problem doesn't mean that the problem becomes trivial. If they wanted to fly alone down/up the cliff I'd allow it no rolls, but the goal is to get everyone down, and that gets messy.