TerastallizationAbsolutely! I try to be available to respond to folks where I can. I've never enjoyed communities where it feels like a huge deal if the creator speaks - I'm just the dude who happened to make this game.
Fakemon: Its super easy to miss, but we do already have a fakemon in the game right now! Castform has a sandstorm variant now. It isn't exactly a super original idea, but I know, but it felt like a no-brainer. Exclusive forms, evolutions, etc are absolutely on the table - but my goal is to use them sparingly. I think the fakemon rabbit hole goes deep haha.
As far as an additional form for Mistress goes - my lips are sealed. I do have all sorts of things planned, but I don't want to show my hand too early.
Plot: I've been sprinkling bits of the plot here and there. The story of this game is being told through many smaller plots. I think if you squint, you might see some loose threads dangling, just begging for me to pull them. For example:
1. The Indigo League is in complete disarray at the moment.
2. Giovanni has just been outed as the Leader of Team Rocket.
3. Lillie/Lusamine...
4. Ariana has something powerful up her sleeve.
5. Something funky is going on with the player character.
6. Nihilego is in Kanto.
7. The Sada subplot.
8. Courtney just called in backup.
9. Everything surrounding Giratina - there's a lot I can flesh out there.
10. Cynthia, at one point, was a Herald.
etc, etc.
I enjoy being able to pull on threads an a nonlinear fashion. As the game progresses, you'll gradually become more intertwined with these stories, and more of the story at large will come into play. I've had things planned for this game for years now that I'm chomping at the bit to get to. One thing I will say, though, is that none of the special (control/possess) mons are required for the main plot. You can skip every single one of them.
Plates: I don't have a ton planned for the Arceus plates, which is why they're all available en masse in the Azure Town Mine. I do think messing with types is a cool idea on paper, but I wonder if Terastallization fits that same niche. Without a visual indicator of types, I fear that a mechanic like that could become extremely frustrating to players if I use it on enemy teams.
Using moves on the opposing trainer: This is a cool idea that has been floated around many times for a unique Control type battle effect. I'm definitely not opposed to the idea of Control types having something special during a battle, but I don't think I've settled on something that I am satisfied with yet. I am giving them a unique way to interact with teambuilding, though, in the same vein as Remnants from the possession mechanic.
Custom Moves: I'm absolutely not afraid of custom moves. Aqua Smack is already in the game to give a physical, no-secondary-effects water type attack to mons who need it.
Anomalies (Super Shinies): I don't have it in me to make 1025+ unique shinies. As awesome as that would be, that would be a massive time sink that would take away so many resources and time from development of other parts of this game for a feature that really doesn't have a huge impact on gameplay or nsfw aspects. That being said, though, I do have a very small-scale version of this feature planned. Definitely stay tuned on that starting with the next major Gym.
Partner Mechanic: This is something that I'm intending to solve with the Innate system and/or by direct buffs to the mon in question. There are a handful of adjusted statlines already present in this game, and the Innates are already tailored to give a second life to just about everyone. One of the reasons this game pushes capturing a lot of mons as hard as it does is so that the player can interact with all of the very diverse sets present in this game. You might find new team members or solutions in very unexpected mons!