Could I pick your brain a little more on the design? I'm spader at spader.zone; if you have time, drop me an email. I promise not to take too much of your time and I'd love to hear from you.
This can get you started:
https://dlang.org/spec/arrays.html
Strings (and arrays) being length/ptr is a freaking enormous win, in simplicity, performance, and overflow bug elimination.
One of D's secret features is that string literals still have a 0 appended to them, even though the length of the string does not include the 0. This makes it super slick to call C functions, like printf, using a string literal for the format string.
I'm baffled why C spends its energy doing things like normalized Unicode identifiers (an abomination) instead of something incredibly useful like length/ptr arrays.