I'm assuming what you're asking is whether there's a way to keep the Meraki DNAT configuration up to date with changes to the WAN IP (as the ISP is provisioning a dynamic IP).
Unless you want to get real fancy with a server constantly running API calls to poll the WAN IP and update the NAT config automatically (not worth it in my opinion), save the hassle and pay the extra money to get a static IP address from your ISP.