I've thought about trying to support something along the lines of Django Templates -> WASM, but the one interesting thing that Blazor does is it also renders the templates on the back-end for those who don't necessarily want to render it on the browser. I think you'd have to consider some sort of templating language, that intermixes nicely with Python. If I remember correctly, Mako was a templating library I used for a project ages back, they focused on letting you for the most part just use standard python for the scripting side of the template engine.

So if I had the time and energy, I'd spend my time looking at something like Mako, maybe even forking it, and making it minimal enough to build into WASM. I assume you mainly want to shove a templating library into WASM and not too much more. The rest you could offload to a smaller JS library your WASM can interface through.

I could be talking off my other end, but this is all spit balling from various things I've read, I'm by no means a total expert.