https://djot.net/ is similar to markdown but supports more things than commonmark while still not having weird edge cases. this may make it easier for different Tangled interfaces to render all of these contents.
tangled wouldn't need to include the inline/raw blocks for html though.
This will be possible pretty soon! We won't focus on supporting more markup languages in near future, but I am working on making the markup content more extensible so third-party implementations can easily add other markup language support.
See
sh.tangled.feed.commentdefinition for example.