I like the idea - but you need hiring managers to post jobs before it will be worthwhile. What is in it for them? Because it sounds to me like a way to voluntary have talent filter my jobs out of their search.
Basically need a Codality for normal companies with reasonable mixture of real world practical problems, and reasonable algorithm questions. Then hopefully the copy cat culture can pick up on that and we’ll have an organic fix to the shitty programming interview puzzle garbage filtering out decent developers who are just fine for most companies.