The thing is that askhistorians is, uniquely among subreddits, both staffed by professionals in the field and heavily moderated. It is an investment by credentialed, dedicated professionals, and would not work otherwise. I think something like that would be highly attractive, but I caution anyone against trying to resurrect it without access to those credentialed, dedicated professionals. Otherwise it becomes shittyaskhistorians but unironically; at worst it would be ancient aliens.