Lots of alternatives... the value add of Android OS...
You could also use BUMP. There are any number of solutions. I've been personally leveraging Dropbox a LOT lately when I want to get something from one place to another - with the advantage that it is so well integrated into EVERY platform I use. Once I copy a file to Dropbox, it is easily available on my Windows machines, on my Android machines, on my iOS machines, on my OS X machines and on my Linux machines. It is easy to get to when I'm on someone ELSE's machine(s). So, Dropbox was my choice for the article mostly because, well - I like Dropbox. I felt like Dropbox would also be among the easiest methods for a neophyte to get their mind around. If you're familiar with these other methods you've described, the odds are you don't need an introductory "How to sideload Android apps" howto. At least, that was my thinking. I could be wrong.
Although I don't understand why you would need root access for any of the methods you describe. Additionally, if you're going to root, you're probably WAY advanced from worrying about how to sideload apps. Can you root without sideloading, anyhow? I guess if you manually root? But most people out there doing roots are using a 1-click root method, I'd guess.
Wait... are you saying the apps that allow you to host a server, like an FTP or Web server, on your Android device require root access?
Sometimes the things that iOS allows that Android requires root access for make no sense to me. I've never looked at any of the server host apps for Android because - well, with the open OS, there isn't a lot of need for them, unlike with iOS. But the idea that you would need to root to do that on an Android seems counter-productive to me... kind of like requiring root to take a screenshot.