Basically it’s broken right now. You can try and fix it and it will either work (yay) or not (so just like now) you have nothing to lose. Worst case you tried something new and learned things!!!
You could potentially modify a game to work with those cards. Making cards able to change state or add extra states (that would usually be extra cards) to a single screen. I like your idea. Maybe the idea would not be a retro fitting but a ground up new mechanics for the mage?
a display driver that connects to that flat ribbon cable to the display.
a MCU or computer to host your programming and send commands to the display driver
power, wether it’s battery, USB, or induction…
You can separate the screen from the driver and have the e paper show the last image. The one thing I’d be worried about is how fragile the components are on the side of the rapper display itself as well as the ribbon cable.
Also, you mention 150+ cards. Think of the time it would take to change each one separately with a dock. Connecting the display to the driver is not hot pluggable you would likely need to power cycle the whole thing at every card. Plus the damage risk of constantly connecting the fragile connectors.
My opinion: look for a new LED flashlight. It will have the proper circuit and design to take advantage of LED capabilities including high brightness, PWM dimming, power efficiency, and heat management. Adapting an incandescent flashlight will always be a compromise in one of those.
Edit: I have a similar flashlight and I bought a tiny usb-c rechargeable flashlight that is brighter for 1/5 of the size. And for battery life, you can recharge your keychain size light with any usb battery pack.
I’ve seen it used on Cinema Camera filters to make funky reflections in the lens.
We were filming a dream sequence and to make the edges of the image soft and blurry, we used an optical flat (a clear filters basically a piece of clear glass that slides in front of the camera’s lens) and the DP (director of Photography, aka the Cinematographer) smeared some Vaseline over the edges of the flat, painting the blurry edges with his finger. It worked really nicely, unfortunately I can’t find the final video online to show the result.