Configure Fluid-based email template paths via TypoScript
The Fluid-based template paths are configured via LocalConfiguration.php. In multi domain setups it could be helpful to setup a template set for each website. Therefor you have to add separate configurations in AdditionalConfiguration with conditions respecting the domain.
On the other side we have the amazing feature called "Site Configuration" and even this brand new 10.4 sub-feature of "Site settings as TypoScript constants". In my opinion it would be a more than consistent way, to use the YAML based site configuration for all the site config stuff and of course for the mail templates. Maybe this thought could be pushed ahead to a general API for doing site configuration overlays?
Thank you for your enthusistic work!