If it's fully static, then it seems like it could be packaged in a lot of easy to install ways that people would really like.
I don't know how important they are, but the stuff I can think of right now:
Base64, hex, qr codes, ASCII codes, and binary are staples of the "things you do by googling a random tool" genre.
I used a polynomial regression calc online one time, it was very helpful, there's probably some really good easy to integrate equation solver libraries out there.
Unit conversion is always good.
Basic electronics calculators might be nice, areas of geometric shapes, etc are always good.
I wonder if there's some sort of generic calculator schema and already existing data that could auto generate some of those hundreds of trivial things that would be tedious to build individually?
What about expanding into "pocket ref" style data lookup? Like, you give it a list of JSON blobs and a schema, and it gives you a nice table view with unit conversions and search.
People could contribute tables for stuff like "What's the max head diameter for a #6 screw" or "How far apart are these metals on the reactivity series".
If it was all built from a folder of JSON files, people could build custom application specific variants to answer questions.
There's a lot of really cool possibilities here!