Deterministic keys with one-way operation
If you use a one-way hash function (ie like hashing ECDSA public key with SHA256/RIPEMD160 into a hex public key) then how can you employ hierarchical deterministic functioning?

You can't. The whole point here is that if you lose your private key for a grandchild public key you can get it back again with the parent key. A two-way hashing function obfuscating the data would work but that's basically what's already in place.