I agree, all services could potentially inject useful env variables.
Also, I agree most will only have one (mine do). That said, all services do already have a 4-character UID, which could be perfect for this purpose:
I have a question for you though — how would you actually use these environment variables?
In Laravel, for example, you could add this to your
...however that will only take effect when you empty the config cache (
php artisan config:cache). Since Indigo may assign a new port (when the port is configured to "auto") any time the stack is started, that would break the site until the config was next cleared.