Adding non-standard APIs would be not be a good decision for the future of a standards compliant OS.
Sorry to respond again. Perhaps I am not understanding properly. Are you proposing another set of APIs or instead proposing to replace the standard APIs with a different implementation.
Replacement of standard OS APIs with architecture specific versions of the same APIs is something that is done in several places in the OS. For example, this is done for several libc functions that can be CPU hogs (like memcpy, strcmp, etc.). This is already done for RISC-V in libs/libc/machine/risc-v. You could simply extend this for the optimized APIs that you want.
That keeps the APIs standard and is very easy to maintain, especially if you were to follow the same pattern. I would recommend that you look into these and see if this approach meets your need.
