Are you Walter Bright, the creator of D? If yes, I was thinking of writing a proposal for WG14 some time in the future regarding slices/fat pointers. Would it be ok if I modelled it after the extension found in the betterC compiler, at least when it comes to syntax?

Yes, that's me. I even wrote an unofficial proposal for C slices!

https://www.digitalmars.com/articles/C-biggest-mistake.html

Feel free to model your work on this and/or on D as you see fit. It'd be great if you made it into an official proposal. That one thing will greatly benefit C programs, much more than any of the other improvements in the C Standard I've seen over the years.

Thank you for your answer and the inspiration! I'll try my best!

I can help with review and defense of it, too.

Note that we are already looking into this. I had some proposals for C23 on how to improve arrays in C, but I could not finish this in time. But help is welcome.

Oh, I didn't know that, nice! Is there some kind of draft of a paper which one can read in order to contribute/help/see the state of the proposal?