I know some of these ideas could possibly take a lot of work to do, but this is more of just a brainstorm thing of some things I've kinda thought about while playing that might be within reason.
Totem-Sized Pokemon Eggs
For those that haven't played Sun/Moon or Ultra Sun/Ultra Moon, there's two types of Pokemon in the game called "
Totem Pokemon". "
Totem Pokemon" are basically larger version of regular Pokemon that have special stats and an ability that lets them summon allies into battle. These basically function as bosses in the game and you can't actually capture them.
In adition to them, there's also a type called "
Totem-Sized Pokemon". These are also larger versions of regular Pokemon, but this is just a cosmetic difference and are otherwise no different to their regular sized counterparts.
I feel like "
Totem-Sized Pokemon" could be a good addition for the Cash Shop and might not be too difficult to implement, since it's a matter of resizing the models for regular Pokemon instead of full redesigns (I might be wrong on that though). Pokemon that are fairly long (like Wailord/Gyarados) might not be the best fit for this because they can already be somewhat obstructing in fights, but others could work alright.
Also, the concept of standard "Totems" could possibly be something to look at for potential rare wild spawns/trainer-like fights that you can't capture but instead battle for items, coins, a few tokens, large amount of XP, etc.
Here's some examples of the size differences between regular and Totem-Sized;
Ball Capsule Seals
In Gen 4, one mechanic that was added that hasn't really been seen since was Seals you can place on Pokeballs. These were basically a little cosmetic effects you could add to Pokeballs that activated when you sent out your Pokemon. There was effects like poofs of stars, flames, bubbles, music notes, clouds, ect.
In terms of the store, I think a mechanic like this can be compared with the sort of lobby PokeWars cosmetics you can get. In fact, the seals could work in a similar crate style.
As for the mechanical implementation, I kind-of feel like this might be something that could potentially work utilizing some of the visual effects already attributed to certain skills, but setting it so these appear on deploying a Pokemon. In my mind it could function like how hats and bikes work. You'd use /seals to open your menu of various Seals (or Seal remover), you select the effect you want, another menu opens where you select the ball slot (1-6) you wish to apply it to, and it's ready.
Here's a video showing the various different Seals in Gen 4;
New Hats
For this I was thinking about maybe a hat line that instead of having hats based on Pokemon, actually having small Pokemon perched on your head. Pichu, Pikachu, Pidgey, Spearow, Cleffa, Clefairy, etc. Some Pokemon could also be put on the back of your head to make it look like it's holding onto your head (with maybe some alterations to the arms when needed).
Here's a screen I took to kinda give an example;
Click to expand...