I think that sounds a bit too advanced. I’m not fully on @janet4now’s side that it’s always unethical to ask for a pre-interview assignment, but it depends a little bit on how useful it seem to be for them, or if it’s just a way to get a controlled view of how you work.
I would not put down more than 8 hours on the assignment.
As someone who got her job based on at least partly the assignment, I know how good they can be. It gives the employer a chance to see how you work, how you think, and innovative you are, as well as how organized you are. However, it should be clear that that’s the purpose, and not that they want to “crowdsource” something they actually need.