I say get one and once its in your hands see what improvements you can come up with. I'd suggest a new one or see if Rob has any Blems not listed. After you get your feet wet with a new, working one then you can dive into Classifieds. Rob sells extra Door magnets on the site and he might even drill a door for you at both ends if you ask him. I can tell you did some homework if you noticed there'd be no magnets if flipped. I look at everything I own with an eye toward improving it. My Reo's included. I replaced the firing pin on my 2.1 with a brass one. It works but there isn't enough gain (if any) to warrant the effort. It was a slow day at work and did pass the time. Now I'm looking at my Reo's with an eye towards modification rather than improvement. I'm going to be attempting some of them soon, mainly cosmetics. Here is a video of some mods a guy did on his, for me I wouldn't consider them improvements but they probably are for him.
Reo Grand Modifications - YouTube
It looks like the springs are compressed on that video with the stacked batteries. I do not know for sure, but if that is so, please for your own safety, do not attempt. The spring is the only safety device on the Reo. It is designed to drop the battery down in the event of over heating of the battery. When you compress the spring with your batteries, it will not terminate the connection in the event of a short. This can result in the need for some costly face reconstruction surgery, or funeral expenses.