First, read this thread. Someone did it and the broody raised six chicks. Since the thread is full of photos it should have some credibility with you.
It’s not a great time for a broody to raise chicks. There is more risk. But as you can see, it can be done. The lady also said she would not do it again.
I don’t know how high that nest is but I’ve seen a hen get chicks out of a ten feet high hay loft. Mama flies to the ground, says jump, and they do. When they land they bounce up and run to Mama. The hen being able to get them down would not concern me at all.
How big is that nest, or more important how close to the edge of the nest is the hen sitting? Baby chicks often like to climb up on Mama’s back while she is hatching the late comers. Of course they fall off. If Mama is away from the edge it’s no big deal. That was fun, I’ll go do it again. But if the nest is small enough that the chick might miss the nest and go all the way to the floor, then I’d have concerns.