Company internal plugin system

Hello everyone,
for last time I was thought about somethink like a WordPress plugin manager for my little CMS system.
I know plugins are components and right way to add some components into project is Composer.
But I talk about internal (company) components like calendar, gallery and many other.
I mean plugin is somethink with controls for frontend and backend (create gallery, show photos…), whitch can do automaticaly add link into admin-panel menu (maybe extension).
How to add this (plugin) or component into the project? Create folder “plugins”? What is the right way?

Thank you for answer.

Sorry for my bad english.