I would also go the separate push/pull API based solution.
Software than plans your address space on it's own and then reads your current org for subnets and push out own addresses per network.
A bit like you have DNA-center carving out subnets for each site in a design section and then creating networks with the IP addresses.
I also don't particularly like the current Meraki template implementation where they choose random subnets for template networks if you have multiple VLAN's.