I just finished reading all 600+ messages in the archives here, in chronological order and it was really enlightening! Thank you for allowing me to be able to easily do that. It's just what I needed to do! I made lots of notes!
A couple of things I'd like to note for you:
1. Having no database is a deal breaker for so many Yahoo Group owners, that if you considered providing that option instead of/or along with the wiki, I think you would find that a lot more groups would want to come here from there.
2. The ability to add members directly is also another deal breaker for many people, and not just as the one time fee thing, (which could be negotiated).
Maybe there could be a way to allow ONLY the group owner to add maybe just 5-10 members per month, or some other semi-reasonable number that might allow you to implement this for free without having the abuse issues of adding a lot at once.
The reason so many Group owners need this add-members feature so badly, is that SO many Yahoo users are elderly, handicapped or both, and not at all tech savvy. One of my own moderators in my MM group has this very problem with the members in her group. So even sending them an invite does not work. -- So this is something I hope you'll consider.
3. Archives in my opinion, should have the ability to remain intact and unedited, if the owner prefers it that way. Other than someone deleting their own posts, which should still be allowed. But that's just my opinion, and isn't a deal breaker for me, as I archive all my own data all the time. But for someone who uses it for say, a research group, they might want it to be static, which maybe could be an option?
Meanwhile, you are rapidly approaching the ability to be an actual viable substitute for most, if not all, Yahoo groups. Trust me, I know. I've been down in the Trench in the Yahoo Feedback Forum. I've been all over Twitter fighting with Jeff Bonaforte himself. I have seen it all, heard it all, all the horror stories, all the losses. Groups.io can be the answer to all of those prayers!
I miss the ability to customize our groups with color and such, but even that is something I can live without because you don't have horrible font color on horrible background color, which was blinding in NEO. Still, it would be nice if the font and background of messages or posting windows were somewhat customizable for vision impaired or affected people to be able to choose the best choices for them. White isn't always the best choice.
I've been trying to rescue the disabled/vision impaired/elderly contingent from Yahoo Groups for over a year now, and told Bonaforte that I would NOT wait 2 years for Yahoo to fix things. So like I said, our rescue ship is on the horizon! And we can't thank you enough.