Really glad to hear that you managed to find and order the orange backlit set that’s to your liking! Looking forward to the pictures 
True about using a blank keycap (or any other 1u keycap) in the same row sculpt as well. 3D printing opens a world of possibilities that you can definitely try out. Perhaps some DIY projects that you and your son can work on together!
Also, after a quick google search, I see that FL980 has some programming software which you can download here: 002-FL980 - Google Drive. I believe you should be able to use it to remap and save the mapping in the keyboard firmware