Create a new tag value source "Development" along with a development mode toggle on/off switch on the Gateway config page (or a bindable tag property - this would allow for multiple sets of "dev" tags based on the memory tag it's bound to).

The Development value source uses both the value (memory) AND OPC path properties. Based on the dev mode toggle switch, uses the value assignment when in dev mode and uses the OPC path when not in dev mode (production mode).

This would allow tags to be created as "memory" tags during development and testing while still being able to assign and inspect the expected OPC path, and then quickly switch all of the tags over to OPC when it comes time for deployment.