I'd like to suggest two features:
The ability to edit the page title tag, url slug and meta description for node indexes and threads. Similar to how to many of the SEO add ons work for wordpress.
For nodes, it would be useful so that the URL and H1 can remain short and concise on site (as is the case with the current ACP options), but then you can still have a long descriptive title tag to show up in the search listings, encouraging users to click.
For example, picking a product off the top of my head, say it was a water discussion site you could have it setup like so:
Nice short URL:
waterforum.com/britta
Short, but still descriptive on page H1 (original node name in the ACP):
Britta Filters
Longer and much more descriptive title tag for serps:
Britta Water Filter Forum & Community
Some custom meta description to act as a CTA for search engines users that you don't really need displayed on the page, vs the current node description which gets displayed on page and in the SERP snippet.
This could also be very useful for specific threads with good content that you want to try and rank.
You don't necessarily want to go around changing the display H1 thread names for all your user's content, but you could have the ability to change and optimise the URL slug and also the hidden title tag and meta description for that thread. This will allow you to front load the URL and title tag with the important keywords, while maintaining the original on page h1 thread title.
Each forum can be set individually 
