"We can't change structs that don't get SROA'ed because of limitations of the language. For one thing, essentially any memory we write to the GPU's global memory can be read from the CPU side, and it's basically impossible to tell what is and isn't read, so we have to keep the memory layout the same. "

Which is precisely a language semantic problem, since there are plenty of languages where you can change SOA to AOS. In fact, it's wildly common among high perf fortran compilers