[juped]

Some interesting ideas here. However, C is being improved in an evolutionary fashion; the latest revision was C18 in 2018. I like languages like this (my favorite is D), but the only C successor language I use is C11 (this is what clang targets; C18 is an incremental minor update to C11 that only fixes errata).

    x = t.1; // extract 2nd tuple element (zero origin)

Zero-based indexing in a programming language is not necessarily a dealbreaker but is always a worrying sign about how hard the designer thought their design through. (This does not apply to the design of C, which does not have zero-based indexing; arrays are indexed by offset rather than "from zero".) These are structs with fewer names and less ceremony involved. Why would the first field be "field 0"?

[retrac]

Modern computers encode the first address of memory as a binary word of all zeros. In an array, a pointer to the array + 0 is the first element. A pointer to the array + 1 is the second element. C is low-level, so it makes sense to follow the machine idiom.