I think if anything, it's not restrictive enough. The idea is that HN acts as a community filter for membership, and 200 is really not much for an active member of the community.
You would need a threshold of course. But having that would also mean there would be a fringe demand for people who are above the threshold.
Thus, if this is done, there could be demand for a job board where non-threshold-meeting HN members can employ threshold-meeting HN members to post their job ads. Ok, partly kidding.