As I had mentioned earlier when you first asked for ideas. Here's a drawing of the PowerGrip. Nothing is to scale in this drawing as I'm new at using this program and don't have AutoCad anymore.
There's a possibility to have a magnifying glass in a frame that fits into the console slot on the grip when not in use. The frame would have foldable left and right supports that could be snapped into mounting holes on each side of the console slot. I'm too tired to draw it at the moment.
Another cool option that could be added is a headphone jack near the USB ports.
The idea is that it can extend the device's battery life, add comfort and provide an option to play with a friend.
Ok, I feel pretty stupid now regarding the magnifying glass part. Since the magnifying glass will have almost the same surface as the actual screen the increase in size would be minimal at best (cropping at worst). But at least I drew it like I intended and I think I'm getting the hang of this drawing app now!
This could be a nested bluetooth controller instead. As far as I know the FunKey S does not have bluetooth, but the PowerGrip could.