I know this may be sacrilege but the OCD monster in me really would like to create application folders on the left side of the dock and have them fan out when I wanted to use them.
For example, having all the Microsoft Office apps in a fan to choose Word, Excel, Powerpoint, etc. Having a fan with easy access to apps like System Preferences, Console, Terminal and Disk Utility. Putting the iOS apps like Music, Photos, Messages and FaceTime in a folder to fan out. Whatever I set the folder icon to be should be displayed in the Dock for that group.
Yes, there are everyday apps like browsers, email and Xcode that I still want explicitly on the dock as individual icons. I know I can have folders to the right, but I prefer to use that space for my project folders, Documents, Downloads and open windows. I would prefer putting the moderately used apps in a place where I can still access them from the Dock without overextending or opening via a Finder window or desktop folder.
PS: What's the deal with Dock spacers? Why do they need to be a full icon width? Can't we have a half-width option?