I don't have suggestions for you, but I do have a question regarding this point. Why wouldn't Java be considered lightweight? Java literally runs on your SIM card, which is a very bare-bones environment to run something on, I'd probably consider something like that pretty lightweight.
When I think about how many stuff needs to be moved in cpu/memory/io bus just to launch simple "Hello, World" in Java - I just cannot accept it. I do realize that for large programs that overhead is small, but still the JVM concept is something I want to avoid as much as possible. Plus the sheer scale of Java SDK and amount of legacy and complexity behind it exceeds my treshold of "avoiding complexity" by orders of magnitude. And the nail to the coffin of "no java" stance is, of course, experience with desktop Java applications. Consistenly the worst UX experience and performance I've seen in 25 years among desktop apps.
Seriously though, I agree. The fact that a file format can stick around that long is impressive.