One note: For truly "responsive" text (and other measures, like padding/margins), I often use relative units of measurement. At the very least, rem/em, but more and more I'm using viewport¹ (including dynamic) and container query² units. I'm not your target market, and I know that owning the renderer makes this request more complex that it would seem, but I thought I'd point it out just in case you think it should be on your radar.
This is something we are going to add for sure. Ideally, we will support any unit (em, rem, %) you can use in CSS for any property we expose like padding or font-size.