WP-Content is one core file that is dangerous to mess with. Probably not as bad as WP-Admin, but still bad and, usually, at the very least, unnecessary! WP-Content contains your themes, plugins and content. If you want to make changes to or add to the functionality of your wordpress site, that’s what plugins are meant for. There are enough of them out there that its likely you’ll find what you need.
The reason it makes more sense to use a plugin is that you don’t prevent your site from being able to update or lose the changes you made to the core if you do upgrade.