I like where you're going with Litements. There are a lot of servers that could just be libraries running on SQLite. Job queues are one of those I find myself reimplementing sometimes.
This is an interesting idea... It'd be really cool to have these as SQLite extensions. I could see that being powerful (in part because of language agnosticism). Granted, a bit harder to build/install. https://sqlite.org/loadext.html
I'm currently working on implementing a set of data structures (and more things later) on top of SQLite (https://github.com/litements/) for some of the same reasons you mention in the article.
I probably don't even have 1/10 of your experience, but your work is really motivating me to keep working on it, thanks!