Personally I disagree with the mix of features / lack of features the OP is going for, but I totally understand the desire to play with some aspect of the brows

Personally I disagree with the mix of features / lack of features the OP is going for, but I totally understand the desire to play with some aspect of the browser to make it fit a long-tail use-case. I wish for a composable set of utilities that can be put together into a browser even if they aren't very good. For instance, I have often wanted to experiment with a CLI browser that had js support. If A platform existed that just allowed me to swap out the renderer with my own thing it would make that dream easier. I'm curious how far one could get by leveraging jsdom inside of node or quickjs. Clearly the result would be compromised, but if it is even slightly usable, it may fill the needs of the OP and other experimenters.