Indeed. Vega has been one of our inspirations. Though, we took a more business use-case focussed approach for the visualizations, and also more focus on performance.
I'm a big fan of vega/altair but the biggest limitation is that it can't scale to larger datasets. It might be interesting if you made some side by side comparisons of implementing examples from the vega gallery using Muze. An Altair like wrapper for python users would be nice too, of course.
https://vega.github.io/vega-lite/examples/#interactive