1) Bring back Slooms as a Danger Mission exclusive enemy, preferably in a brand new one. Then to keep Zee Cores rare, make them a 5* mat. Maybe in the future they could be used for like one or two recipes.
2) Rare Colors. Height and eye changers both have rare variations that are mostly only found in mirrored lockboxes. Why not colors too? Possibilities:
Pastel colors (not necessarily light variations of all 24 colors - just at least the 6 or maybe 12 most basic ones)
Gray, Silver (pale gray) and White
Slow, Medium, and Fast Prism (cycles through the 24 rainbow colors at various speeds, probably not taking less than 5 seconds for fast though, so not like eye-assaulting Geocities-GIF-like rainbow blinking) - probably should be like the rarest item ever
3) Open up the last bit of Jelly Farm! Replace the enemies in it if that was the reason it was closed. Inaccessible rooms are super lame. :c
4) Add at least one more 0* and 1* bombs in a little crafting chain. Yes, I know this is sort of a weird thing to suggest, but hey, we got Robo Wreckers a while ago. And my Proto Bomb is jealous of my Proto Sword and Proto Gun because they have 0* friends and he's all alone because the 1* bombs are all like "we're too cool to hang out with you".
5) So like... Blast Network is like "Bombs: The Game". Why not add more PvP that is like "Swords: The Game" or "Guns: The Game"? What I mean is, games where you are given a specific weapon and nobody has gear advantages.
6) As a suggestion for the sword game... since BN is clearly based on Bomberman, why not base it on some other super awesome multiplayer thing? Specifically, I'm thinking like Checkerboard Chase from Kirby 64. So instead of hitting each other with swords, the swords attack the floor itself (Troika-style), and try to make the players fall down when the floor does.
7) And, as a suggestion for the gun game... well, actually, BN but with guns would be pretty cool. But maybe instead of a shooting-other-people game, you could have a target-shooting type thing.
8) A new helmet or costume helmet that looks like a parka hood, with fluff around the edge and everything. :3
9) Fix the bug where when you're using a Heat Amp, it doesn't show the correct amount of heat gained... maybe by counting it after the regular heat has been distributed, instead of at the same time.
10) How come all of the HoH vendors have basic eyes? They need some variation. And Sylvan should totally have happy eyes.
11) Heart eyes! Maybe around next February you could introduce them. Also, triangular, diamond, and square eyes. And maybe crown-shaped eyes as the Cradle-themed version of the "dollar-sign-eyes" cartoon look.
12) More beast-type enemies. Maybe some humanoid ones. Also, another turret type - of the three, two are weak to elemental, one to shadow, and none to piercing. So a beast-type or fiend-type turret would be good, if you could figure out how to theme it. Maybe a snake in a jar for a beast turret? It could have close-range bite attacks in addition to spitting projectiles, to make it unique.
13) Replace the Jelly Gem armor rewards (mundane armors that can be crafted anyway) with something more unique. Maybe a toxigel armor line? It could be a green version of the Quicksilver line, and have poison resistance instead of shock. Or an oiler armor line, black and resistant to fire. Or even a toxoil line, resistant to both!
Beasts could certainly use some expansion as an enemy caste - Wolvers simply aren't a significant threats, and whilst high-level Cromalisk variants can be a headache, the entire Beast family still comprises two (!) enemy types with a handful of variant skins. I dunno if a turret fits the theme - I think it'd probably seem rather forced - but a Fiend turret would be...well, not exactly welcome (Fiends are already a huge headache), but variety is always appreciated.
Agreed agreed agreed about the Jelly Gem armour selection. Boss token rewards should be unique items; either replace the armour with something new, or remove the set from the HoH. I like the Oiler idea a lot.