I think the only thing this is missing from Foreman is .env file support. I can use dotenv to load it up within my app, but I'd prefer it to be in the environment on boot. Also, it would be nice if we didn't need to specify a config file and would just auto-search for an invoker.ini or Procfile. Saves some keystrokes and makes your CLI a little nicer.
Although undocumented but Invoker does support .env files. It should detect and load if any of the directories contain a .env file. Please open issues if it does not work as expected.
Since it's not documented, the support for .env is unexpected!
I looked for a way to fork and update your documentation but didn't see one.