Yeah, I know raw audio data like that would balloon really quickly. But on all those old CD-ROMs like The Manhole, raw audio was the norm. Back then the bitdepth/sample rate was your compression, I guess. So I don't really care about compressing the audio. For a standalone desktop deck it wouldn't be so bad, but I wonder if a 500 mb deck (hypothetical rough "CD-ROM" size) would struggle to play in a browser. I really don't know.
It would also be interesting to have small postage-stamp sized QuickTime videos (dunno if QuickTime itself is usable, probably proprietary) you could paste in as an opaque string.
But yeah, you can check out a manifesto/document I made years ago about my general idea for bringing back this HyperCard/Director aesthetic: https://artfluids.itch.io/directorcore-manifesto
It doesn't fully reflect my feelings on the topic anymore, but the general gist is still how I feel. Decker is the closest thing I've found yet to this ideal.
I also want to say that I really like Lil. I was going to get into the nitty gritty of Flex/Bison to make a parser for a similar HyperTalk inspired language, but I think in the future I might just borrow Lil and use your parser. If I do, I'll let you know.
I think it is worth looking into aspects of Macromedia Director because it is very inspired by HyperCard. Its programming language, LINGO is almost like a dialect of HyperTalk.
I know that if the scope of this project gets too big then it loses its appeal and charm. But for my part, I think for it to become a real "multimedia sketchpad" it would have to embrace the Macromedia Director phase of the Macintosh as well (at least up until like 1995. Director 4.0). Maybe have videos. I'm not saying it should have every feature of Director. Because Director had stuff like timelines (individual frames could have their own scripts, just like cards/widgets) and that starts to scare away newcomers/non-programmers. I just think the aesthetics of Director would be nice (i.e. 8-bit color, video, 22.01khz audio).
But, all that said, I am thrilled to find Decker and am excited to use it as-is. Also, I'm spreading the word to anyone who will listen.