I think this is an interesting idea, but I also somewhat suspect you've replaced a tedious problem with a harder, more tedious problem.
Take your idea further. Now I've got 100 agents, and 100 PRs, and some small percentage of them are decent. The task went from "implement a feature" to "review 100 PRs and select the best one".
Even assuming you can ditch 50 percent right off the bat as trash... Reviewing 50 potentially buggy implementations of a feature and selecting the best genuinely sounds worse than just writing the solution.
Worse... If you haven't solved the problem before anyways, you're woefully unqualified as a reviewer.
Take your idea further. Now I've got 100 agents, and 100 PRs, and some small percentage of them are decent. The task went from "implement a feature" to "review 100 PRs and select the best one".
Even assuming you can ditch 50 percent right off the bat as trash... Reviewing 50 potentially buggy implementations of a feature and selecting the best genuinely sounds worse than just writing the solution.
Worse... If you haven't solved the problem before anyways, you're woefully unqualified as a reviewer.