General information on every pet/owner in Nintendogs + Cats is documented on the Characters page, but the missing 7 NPCs are really something else. I honestly wouldn’t know what they could be besides scrapped material, as well as the 3 extra tricks on the other NPC’s pet data. I know that there are 17 tricks players can teach their dogs, but you mentioned 20. Could that mean there were additional tricks planned to be in the game but were also scrapped for whatever reason? Seeing that they have placeholder names, it makes me wonder what they could’ve been.
Ellie is similar to Ted Rumsworth in the sense that she cannot be found on walks or at the parks. Still, her pets can be seen in-game. Her dog Sam can only be found in competitions and her cat Precious can be interacted with at Café Petrov. Cats cannot learn tricks so it makes sense that some of his data is blank. Ted Rumsworth’s pet Cleo must also be a cat… which surprises me, as there isn’t a cat named Cleo anywhere in the final game (at least in the US version, I am not sure about the JP version). However, there is a Cleo in the demo version, and there are images of her. Would it be possible for you to load Cleo’s pet data to see if it is in fact the same Cleo from the demo, just to confirm?
We do have a Mii article on the wiki, and expanding upon it would be great. I looked up the staff credits for the game– sure enough, there is Rina Yamauchi under Planning and Daisuke Kageyama under Design Director. I will have to add the creator names to the article, perhaps as trivia. I can also make a chart for the 29 Miis along with their corresponding file name. Maybe good-quality images of them, like the one you have of Ted there, can be added to the page as well (you would be given credit). I’m guessing the other 100 Miis are just the ones that pass by on the sidewalks in-game, so I don’t think a chart is necessary but I can mention them briefly.
Thank you for everything you’ve managed to discover thus far, it was interesting to read! I admire your dedication to preserving Mii data and ensuring it does not get lost to time. Let's be hopeful that someone will eventually come forward with the SpotPass data.