In reply to Ahmad Awais.

Hi Ahmad, thanks for your answer and the work you put in the toolkit.

Would you say it's technically not possible to build the blocks inside a theme? More complicated? Or is it just a preference?

Having about 60 active Wordpress sites online at the moment, most of them use a few lines of PHP inside the theme itself to create meta boxes. Even though I understand the reasoning for putting meta boxes inside a plugin, for my use case it's better to put everything in the theme. They are themes specifically build for clients, not distributed. So I prefer everything to be in one place.