Why the Plank is Sarco on Jakku?

So, as I imagine anyone who reads this has been, I've been playing Battlefront in nearly all of my free time since its release, but I decided to take a break (albeit a small one) to discuss something that's been gnawing at me since finishing Weapon of a Jedi a while ago (if you haven't read it yet, uh, spoilers incoming):  What is Sarco Plank doing on Jakku? And why is he more than just a throwaway character used as a plot device to help advance Luke's Jedi training? Why is he so important that he gets a databank entry and an action figure? (Okay, granted, neither of those things really make you an important character, but, this early, it seems telling to me.) Are Sarco and Luke going to meet again? Is something going to happen to make Luke regret not finishing Sarco off? He's a really interesting, visually appealing character, so I can certainly see, after creating him for The Force Awakens, wanting to flesh him out a little more based solely on his badass appearance, but is that really all there is to it? I'm guessing not...

Let's Get Quizzical! ...About Inquisitors

Alright, so, if it were actually something with which one could be afflicted, I would certainly be diagnosed with Inquisitorius Obsessedius...but, since that's fake, let's just say I'm full-on obsessed with the new canon Inquisitorius (which is a fancy name for the cog in the Imperial machine that includes the Force-using darksiders trained to dispatch Order 66 leftovers). My most recent musings center around who actually trains the brothers and sisters (Inquisitors...I am your father!)...anyway, according to Wookieepedia (with a reference to Star Wars Rebels: Visual Guide, Epic Battles), Darth Vader trains them, but I don't necessarily think that's the whole truth (much like Obi-wan tells Luke that Yoda was the Jedi Master that instructed him...it's not exactly correct, but it's the easy answer). I can certainly see Vader being the supervisor of their training, and their ultimate master, but I feel like he's too important and too busy (see his involvement in Tarkin and Lords of the Sith, for example) to be solely responsible for their daily instruction...so, who else could be putting them through their paces and teaching them limited Force abilities and spinning double-bladed lightsaber technique? I'm so glad you asked! Here are my harebrained theories, see how off the rocker you think they are...