I agree with all of this.
I am one of the few FH "veterans" who has been around since 2012-ish (I can't recall exactly, but I've been here a long time).
There are a few questions that arise that there are new members who have been around since general chat has been already taken out, and so it would be odd. While I agree with this, you may be forgetting of another form that it's still accessible: Private maps.
While you're unable to use General in public maps such as The Grounds, being taken by your roleplay group to their downloaded maps still allow you to use it. So it's not like it's totally foreign for those who haven't been around at the original time when General Chat was still available everywhere else.
Would General chat be misused again at the cost of it being re-open? There's no avoiding that. But we can't forget that even today in The Grounds there are a few people every now and then who think it's amusing to make inappropriate remarks. Keep in mind that in the long run of being in The Grounds, everyone is sitting around the vicinity of its entrance so that they might hear the odd small talk or person that tries to do things the old-fashioned way and advertise in Local. So really, it's not that much of a difference as to if General was still around. Yes, you can turn off General chat, but do one better for everyone else: Get into the habit of cracking down on it and gather those screenshots for reports so that those types of events can be avoided. I really think that's one of the biggest overlooked issues that would follow General's return because 85% of the time I see "Just turn off General" instead of legitimately dealing and potentially fixing the problem long-term. We'd need to protect its vitalness of advertising and keeping in touch with others across the map to avoid lag by assisting to help keep the trolls out of it. Prove that we can handle that it's back. Don't just avoid it!
As for fixed registration times, I believe that, even for a time of "experimenting" with this, would be beneficial. There have been a lot of disputes in the past about whether or not the community is smaller, but if you look realistically at the top of the "Home" page as to how many people are online, there's no argument. There were days when FH reached over 600 people online. Now, at the most, I see 350-450 on average. Correct me if I'm wrong, but I think it's generally around that number now.
It's true that eventually all communities, like it or not, eventually begin to die off. That's just being realistic. We cannot deny this. People grow older. Most of those who were teenagers or early adults back in 2011-2012 times are long gone now, but that doesn't mean there's still an opportunity to keep it alive for the sake of a game that we truly love. We must always bear an open mind and think of both the long-term benefits and downfalls, especially if the community that you've built voices a generalized opinion on how they'd act on it. Game updates could definitely help, sure, but we can't forget about the big picture and what really keeps a game alive: Dedicated and new players alike.
Just my thoughts on this. c:
Apologies this reply was a bit late - I got caught up in finishing college stuff and then job hunting.