So, basically a modified version of the current GTX0 software, with a few additional caveats:
Registrations required, but posting usernames separate for future altname ideas. This would reflect in the people/etc tab as well since there aren't guests in a traditional sense. Guest posting might be a module, but usernames can't be claimed by passwords.
Highly modular. A lot of things will need to be customizable to different branches or just changeable.
Sane CSS controls, possibly with a tool to easily alter them and possibly optional module integration as well.
An entirely separate database/tool for scraping. Need to keep this very separate until the time for Careful Merging.
Usernames on the left. An option might also work.
No true distinction for OPs, or this could be a module with the GT way not the default.
Breadcrumb navigation, and no Quicklinks.
Real-time integration across the board, and ease of posting and editing.
Loose feeds. Forums may have subforums and they may also have distinct branches so there should be a lot of customizability inherent in it.
Robust chat-style private messaging with also larger displays. I think this would be a major selling point-- make it like social media almost.
Similarly, a kind of Journal system for articles or short posts (with followable Feeds/Reshares/Post integration) to tie into the SM aesthetic.
Threads can be subdivided exactly once into "conversations" that can be aggregated in a thread in various ways depending on engagement and/or personal preference.
Private messaging / chat windows can similarly be subdivided like this, so you can have multiple conversations with the same person or aggregate them, depending on preference.
The former point should fix the confusion of forum software while also not going into even more confusing reddit territory. Social media seems to be moving in this direction, just with weaker Aggregation options.