I have a suggestion. A Serperior TF with the "Grass Whistle" theme.

-"Dream Eater"
Gengar Or some other Psych/ghost type pokemon?
-An eeveelution
I like flareon ^-^
-"Thunder Stone"
Not jolteon
just some suggestions XD

I've already picked which pokemon to choose for those pictures, I just tried to build some hype for those.
Thunder Stone was Jolteon, sorry should edit this more often.

But Gengar and Flareon are nice suggestion.

yes ^-^
i hope one of them are chosen
^-^

Still taking suggestions? :3

The idea is to take as much as possible this summer. Then eventualy finish what's left behind later

Alright. I'm not sure if you need any ideas apart from the ones written in your list but:
- "Stealth Rocks" themed tf, maybe something like a damned circle of floating rocks that transformed someone
- Tangrowth tf in the jungles
- A power belt that tf'd someone into Machamp perhaps?

Porygon TF to be able to enter the digital world without destruction of one's original consciousness (the Pokemon episode be damned).
Klefki TF to be used as a skeleton key for Team Rocket

Perhaps some ideas would be:

Lati TF, where a person is changed to a Lati of the opposite gender than the one causing it, kinda to become siblings.
Gabite - a miner obsessing over some gems they find.
Treecko - a person is cursed by the forest/Sceptile/Xerneas after causing damage to the forest
Keldeo - someone being adopted/accepted into the Swords of Justice with Cobalion, Virizion and Terrakion
(Optional Shiny) Poipole - Falling through an Ultra Wormhole and then touching a puddle that actually came from a Naganadel
Rayquaza - climbing Sky Tower, and now having to take care of it after reaching the top
Totodile/Croconaw - Falling into a swamp that has been contaminated
Jolitk/Galvantula - Getting trapped in a web
Porygon - Interacting with an infected computer interface or digital world experiment
Lanturn - A diver going too deep into the ocean
Lugia - Grabbing a Silver Wing that fell from a Lugia
Beldum/Metang - Caused by a Metagross, and that's how they reproduce XD
Honedge - Someone attempting to grab an ancient sword, which is actually an Aegislash
Zekrom - Reshiram needs someone to balance them
Trapinch - Getting trapped in the sand, and changing as they sink.