Following PLANET-6210 to assess feasibility of suggested approaches, we can build two PoCs to check feasibility and make a more informed decision. This ticket is for investigating the 2nd PoC.

Proof of Concept #2: Blocks as a theme feature

Assumption: Blocks can be part of the theme. No need for a plugin at all.

Scenario: Create a new master-theme branch and add a simple block into that. This can be either a dummy new block or one of our existing ones (eg. Guestbook).

1. Would this change be transparent for the editors?
2. What changes would it require to current theme setup (eg. autoload, webpack).
3. Could we have a feature flag for disabling all blocks? (eg. for non-Gutenberg websites).