2024 CFP: Exotically sized types before 2027

well, I strongly think that when Rust supports scalable vectors, it should support them inside structs so we can have an ArrayVec-like type with support for user-selectable vector length (distinct from scalable vector length, which is cpu-designer selectable). (unrelated to exotically-sized types, but important when considering portable-simd design: we should be careful to support user-selectable vector length with a fixed-size (optionally user-selectable) backing simd type, which is what Libre-SOC's SimpleV's native vector types are)