If you're up at that code revision, I've just been typing 'gu' (I believe short for 'guestshell') to get it going. I've never done that iox thing...
Cat9KSwitch# gu
Either you'll need to have the DHCP server on the network where the devices will be ZTP, or use an appropriate DHCP forwarding service (e.g. ip helper-address on an SVI) in order to forward the BOOTP traffic to a DHCP server on a different network. ...