Two that I think would be both useful and popular (i.e. might get Fibery some buzz/traffic) would be:
1. Product/Market Fit Analysis
An implementation of the Product/Market Fit evaluation/analysis from Superhuman, which is now widely used by many startups. Coda version and link to article that describes it here:
I have already talked to @Chr1sG about this one and had planned to implement myself, but havenât had time. 
But it is definitely popular right now, and could get some more startups into the fold if Fibery had a competing out-of-the-box implementation to Coda.
2. Work Prioritization Models (multiple)
Implementations of popular development prioritization strategies, e.g. RICE, etc. I know some of this already exists, but it would be nice to have multiple different ones, and ideally as stand-alone as possible (i.e. with the greatest possible capability to integrate to existing company setups). An existing product that focuses entirely on this, and costs a fair bit on its own given it doesnât have full task management, etc. (it integrates with Jira, ClickUp, etc. for that) is Ducalis:
At the least that is a good overview of the most well-known strategies, although not ranked by popularity/importance (which youâd probably want to do, to avoid having to implement them all). Not all would necessarily be easy to implement, either, e.g. Fibery doesnât have a âquadrantâ view yet (though a Graph view might work?), so doing an Eisenhower-like approach might be challenging.