Contrary to the common belief, Papyoo, Kabiin, and Buhii don’t belong in Capsule Monsters; the sheets they appear on are already titled “Pokémon” and Game Freak’s final logo is on it. We have some similar 1991 GF sheets from Jerry Boy (Smart Ball) and they have a different layout with a different GF script. Additionally, the first known dated GF logo is the unused one in Pulseman (1994). Check out our Lost Pokémon dossier for more info about the placeholder Pokémon.
In 2015 Ken Sugimori posted on his Twitter account the preparatory sketches he made for the sprite designs of the original 8 Kanto Gym Leaders. You can see his original tweets here. As you can see, if the numbering refers to the actual progression of the Gyms, the first Gym Leader was supposed to be a young trainer, possibly the original Viridian Gym leader, scrapped in the final version of the game and “replaced” by Giovanni. Also, although Sabrina’s number is not visible, we can assume she is labeled , and was supposed to be the last.
You can definitely see Blaine’s first design (also featured in the original character mug shots by Sugimori and in the Pokémon anime) later replaced with the current sprite (you can read our theory about this on our Twitter). Koga’s number [6′] might mean that at the time they were considering a couple of different designs for him as some further enhancement of Sugimori’s photos might prove.