After using three decks, I realized that there is something I would have included when i made the decks, if I had made them. 2 to 5 blank cards, for users of the deck to make their own cards.
About 8 years ago, give or take, I was talking with a company about making guitar flash cards. I was taking guitar lessons at their Southfield MI store. The instructor I had suggested making flash cards, for the different cords he was teaching me. Everyone he had would use 3x5 cards, make rough drawings of the guitar neck, and indicate which strings were held down, which were open, and which were not strummed when playing. Being the geek I am, I was able to use Viso to make them. They printed out really nice. Then I printed a few blank ones, so I could take notes, and make new cords on, when I learned them. The instructor saw them, because I kept them in my music folder, and took them to the store's education manager. I made about 10 prototype decks, even laminated those. The instructor took some and gave them to his other students. They really liked them. The manager took it up the food chain. The last I heard they were going through legal to see if there would be any problem printing them and selling them nation wide. Problem is, I stopped taking lessons (the instructor left) and the store closed (they went bankrupt).
The one thing that everyone liked was the blank cards. It was just the guitar fret board, which people could draw things on. I've seen other card decks (Munchkin) do similar things (the blank cards). Actually that might have been where I got the idea from, I don't remember anymore.
It would be great to have a few blank FitDeck cards per deck, which had the same layout as the other cards (different color card from all the others) with the level bubbles, exercise description area.
I know I'd add Burpees to the body weight deck, some more push-ups to the combat deck, and then Snatches and Turkish Get Ups to kettlebell deck. I'd have to figure out what deck to put pistols into.