This would be awesome! The only thing like this that seems to have been made is the Iris v2/Centralite/Xfinity keypad (I think they’re all more or less the same, some upside down compared to others) or the (short-lived) Iris v3 keypad, many of which have different firmware versions and slightly varying features that have made support on some hubs difficult to achieve—and safe to say most of those won’t be getting any more updates. Those were all just battery keypads, no relay or contacts, and I’d be quite happy if that’s all this hypothetical keypad were to be, too, but I certainly see the potential for the additional uses.
A current, supported Z-Wave (or Zigbee, but I’m guessing that won’t fly here 
) keypad that could be used for any purpose — opening a non-keypad smart lock or garage door (honestly any garage I’ve seen would need to be rewired to use this on the outside and considering someone could just rip it off and touch the two wires together I’m not sure I’d want to, so…back to me not caring whether it has extra terminals, haha), arming/disarming your hub’s security/intrusion system, or whatever — would be excellent!