Should we integrate Flysystem

I don't know about anyone else, but it kind of worries me this was even considered. It goes against everything CI has been built to be.

I'm curious - why do you feel that way? And what do see CI having been built to be?

I've always seen CI as a framework with the absolute basics to get you going.. I see it as a framework that lies between a Silex/Slim and a Laravel/Cake. If I wanted a framework that has a bunch of stuff already built in and is more opinionated, I'd be using Laravel. There I'd get all the bells and whistles with auth, queues, etc, etc.

Just as it says on the landing page:

"CodeIgniter is a powerful PHP framework with a very small footprint, built for developers who need a simple and elegant toolkit to create full-featured web applications."

As soon as you start adding 3rd party tools, it's no longer 'simple' because you are depending on a 3rd party to keep the code well designed as well. And with the popularity of Composer and Packagist, there should be no reason someone can't implement FlySystem fairly quickly on their own.

Added:
At the end of the day, if you're going to start adding 3rd party packages, we're just slowly moving towards the more 'bloated' frameworks around. While there is nothing wrong with that, I feel that CI would lose a competitive edge. I'd almost be more inclined to have CI have all of its libraries, helpers, and such be packages that we could pull into whatever application we use.

Codeigniter is simply one of the tools you need to learn to be a successful developer. Always add more tools to your coding arsenal!