Thanks for the pointers, @encukou! Based on your suggestion, I came up with an implementation for sys.abi_info.
For now, I have only added the core three properties, though adding further ones is rather straight-forward.
Regarding the wheel next variants, I think it could be a good idea to align with this by declaring a special namespace, say builtin, interpreter, or, indeed, abi_info, which would allow us to refer to the pieces of abi information as, e.g. builtin :: pointer_size :: 32 and similar for purposes of packaging.