What is stopping you from moving your current Distribution Point to a DMZ and making it publicly addressable? As far as using Jamf Cloud's Distribution Point specifically with on Prem Jamf, that is not possible.
@ngulick As @AJPinto already replied, using JCDS isn't itself possible to use as a DP, but you can use an AWS S3 bucket as Cloud based DP.
What's probably much easier, and what I used prior to switching to Jamf Cloud hosting which provides JCDS, is setting up an HTTPS server in your DMZ (don't ask to set up an Internet facing DP or your InfoSec team should instantly deny the request) that is synchronized with your on-prem DP.
Thanks very much for the replies, I guess we are going to attempt to use Jamf Sync to keep our on Prem package server and JCDS in sync. We run pretty heavy deployments, so I gather that was why the call was made to have the on premise be the primary package server. All good tips. Anyone have experience with Jamf Sync?