Many local resources have been removed on the basis that they were added by an overzealous contributor without the involvement of the people maintaining the resource, or because they are no longer active. Naturally, the level of activity expected of a local group is somewhat lower than that of a national or international group, and there isn’t a firm cutoff. We’re talking about groups typically maintained by one or two people as a hobby. There are far too many of them for a body like the CWG to assess individually, but the stakes are quite low, since very few people will see a given local group.
By the way, the index’s coverage of local meetups (either online or in person) is arguably more valuable to newcomers than the coverage of chatrooms. Traditionally, OSM encourages mappers to get out and survey, and a local meetup can be a key factor in encouraging that kind of activity. More than once, a mapper called into my local meetup from India (because it’s in Silicon Valley 
) and was thrilled to learn that there’s a local meetup in their part of India too. It immediately expanded their perception of OSM’s seriousness as a project.
Unfortunately, by far the most common platform for organizing OSM meetups is Meetup.com. Besides being proprietary and expensive, Meetup also facilitates cybersquatting, which can make it difficult to tell whether a group is still being run by and for the OSM community or whether it’s just a vehicle for e-mail harvesting.
Some Meetup groups undoubtedly benefit from exposure to local non-mappers looking for something to do, but I think many would be content with simply managing their events on OSMCal, which is run by the OSM community. Ideally, iD would list upcoming events by local groups, making it unnecessary for these groups to maintain more than, say, a wiki page.
But probably not at the top, as you suggested, unless there’s some solution for the usability issues for inexperienced newcomers. This screen isn’t a replacement for one’s personal browser bookmarks, after all.
Unless we expect such an instance to serve a significant existing user base, why not instead focus those OSMF resources on enabling Discourse Chat on this Discourse instance, which already has a large user base, plenty of daily activity, and community-approved moderators who may be willing to help out? As far as I can tell, it would meet most of your personal criteria for an upstanding service, but the user experience would be similar enough to those proprietary services that it might actually shift some activity toward this open-source platform.