Something based on the block prefix? So that mods that do support blueprints can explicitly say so, and the architect can avoid registering blocks not explicitely supported.

Could be an API, maybe.

There's definitely gonna be an API component to this.

To be added too - a config setting for opt-in and opt-out blocks from certain mods, to make it easier for servers and mod packs.

Okay, time to update my Smiley Gem Mod then. I'll be using this new feature to add my blocks to the whitelist.