For my second set of suggestions, I think I'll move away from suggesting new items, and instead opt for suggesting updates to existing items. There are quite a few cool armor sets that I feel like are slightly outdated, some of which because they haven't been given Level 150 versions yet, others because they haven't been able to keep up with the power creep of more recent releases. In any case, these are a few changes I'd make:
Set 1: Nemesis Set
Changes: Give a fully-offensive lean. Add level 150 version. Speed up armor attack animation to take less time. Increase resistances to be in line with other
Set 2: Solaris Set
Changes: This one probably needs the least amount of change. At most, all that would be needed is adding a level 150 tier, possibly buff the light resistance ever so slightly to be comparable to more recent light armors. (E.g. buff 48% resistance on the level 130 tier to 44%.)
Set 3: Nova Knight set
The Nova Knight equipment is really cool, but IIRC comes from a time before mastercraft was really a thing. It's a shame too, because I really love the design and wish it were more viable.
Changes: Give an offensive lean, and add a level 150 tier. Buff fire/earth resistance slightly (e.g. 47% each on level 130 tier to 45% each on the level 130 tier.) If it's necessary, make it mastercraft to justify the additional compression resistance.
Set 4: Jester Armor
This armor could be a really interesting and useful option for people looking for a fully-offensive compression armor, provided they can spare the Z-Tokens. Unfortunately, there is one thing with this armor that kills its usefulness, and that's the fact that it's non-mastercraft, which gives it a 5% damage penalty. As a result it's not really worth spending any real money on.
Changes: Make it mastercraft, removing the damage penalty in exchange for a higher Z-token price. That's really all it needs.
Set 5: Gatekeeper Armor
Another armor set from the Z-token shop, this one could actually be really powerful and worth the cost, but there's really only a single thing keeping it from being useful at all.
Changes: Give it either an offensive lean. Defensive lean could also work, but its abilities will likely be less useful with defensive builds due to the power afforded by the Neko subrace armors. Either way, any lean given to it could justify the price.