I've briefly explained the general idea here: https://forums.spiralknights.com/de/node/125670#comment-1079379
This is going to be a more fleshed-out version, mentioning every armor set you can buy in the Hall of Heroes, as well as their SL versions. I'll be starting with Jorin and working my way clockwise, in case people are looking for specific armor sets.
I'll be listing the stats that each individual armor piece should receive, meaning these bonuses would be doubled when wearing the full set.
Jorin:
The entire Cobalt line is underwhelming due to not having any bonuses. The fact that it has Piercing gives it "character," which I guess isn't what this armor is supposed to have. The Almirian Crusader SL armor quite literally results in a net change of zero in the status resistance department.
Cobalt: Remove Piercing.
Solid Cobalt: Remove Piercing.
Mighty Cobalt: Remove Piercing; add Universal Charge Time Reduction Low.
Azure: Remove Piercing; add Universal Charge Time Reduction Medium.
Almirian Crusader: Remove Shadow; set status resistances to Poison, Fire, Freeze, and Shock -1; add Universal Charge Time Reduction Medium and Universal Damage Medium.
Daxen:
With the existence of Padded armor, this is going to be somewhat complicated to do without accidentally making copies of those sets, but I'll try my best.
The three classes; Sword, Gun, and Bomb, each have their own armor sets, so why is it that two of them have Piercing, and none of them have Shadow Defense in the early stages?
While I made Deadshot "the Vana armor" and Shadowsun a "boring upgrade to the 3- and 4-star versions," I just winged it with the other two, basically just having them do something.
Gunslinger: Remove Piercing; add Shadow; remove Gun Attack Speed Increased Low; add Gun Damage Low.
Sunset: Remove Piercing; add Shadow; remove Gun Attack Speed Increased Low; add Gun Damage Medium.
Deadshot: Remove Curse; add Fire and Negative Stun; remove Gun Attack Speed Increased Low; add Gun Damage Low and Damage Bonus vs. Undead Medium.
Justifier: Add Negative Poison and Freeze; change Gun Damage to High; add Gun Attack Speed Increased Low.
Nameless: Add Negative Fire and Stun; add Gun Damage Medium.
Shadowsun: Remove Toxin; add Gun Damage High.
Remi:
With Bombs, I honestly don't see much I can do. Mad Bomber is basically already the best armor you could want for Bombs. You only need a single Bomb Damage Trinket to max out all Bomb stats with it, at the obvious cost of status resistances. So this will be more of an attempt to get the others closer to Mad Bomber.
Spiral Demo: Unchanged.
Fused Demo: Unchanged.
Heavy Demo: Change Bomb Charge Time Reduction to Medium.
Bombastic: Add Negative Fire; change Bomb Damage Bonus to High.
Mad Bomber: Unchanged.
Volcanic: Add Negative Toxin and Bomb Damage Bonus Low.
Mercurial: Add Negative Curse; change Bomb Damage Bonus to High.
Padded Demo: Unchanged.
Quilted Demo: Change Bomb Charge Time Reduction to Medium.
Starlit: Remove Damage Bonus vs. Slime; add Bomb Damage Bonus vs. Slime High.
Echo:
My main objective with these is going to be to have each armor set focus on one stat. Currently, three of the four Wolver armor sets provide a Damage Bonus. I'm also going to include the Barbarous Thorn Shield here, since it's kind of part of the Snarbolax armor set.
Wolver: Unchanged.
Dusker: Unchanged.
Ash Tail: Change Sword Damage Bonus to Medium.
Skolver: Add Negative Toxin; change Sword Damage Bonus to High.
Vog Cub: Add Negative Electric; change Sword Attack Speed Bonus to High.
Snarbolax: Remove Cold; add Negative Fire and Curse; remove Sword Damage Bonus; add Sword Charge Time Reduction Medium and Movement Speed Increased Low.
Bristling, Twisted, and Dark Thorn: Add Negative Fire and Curse; add Bomb Damage Bonus Low.
Barbarous Thorn Shield: Add Negative Fire and Curse; add Bomb Damage Bonus Medium.
Padded Hunting: Unchanged.
Quilted Hunting: Unchanged.
Starlit: Remove Sword Damage Bonus; add Sword Damage Bonus vs. Slime High.
Izola:
Plate armor is trash thanks to the negative Attack Speed.
Spiral Plate: Remove Universal Attack Speed Reduction and Stun.
Boosted Plate: Remove Universal Attack Speed Reduction and Stun.
Heavy Plate: Remove Universal Attack Speed Reduction and Stun.
Ironmight: Remove Universal Attack Speed Reduction and Stun.
Volcanic: Remove Universal Attack Speed Reduction and Stun.
Zebulon:
Zebulon has a lot going on, and in the grand scheme of things, all their armor sets do nothing. Rather than listing the changes, I will list their new stat profiles.
Dragon Scale will become the true C42 armor it was always meant to be.
Who else forgot Silvermail is even a thing? Anyway, let's give it a helmet and make it the Ghosts in the Machine armor.
I like the theme of Angelic armor, but overall, it fails at being useful anywhere. Let's change that by making one of the sets a Vana armor set and another one a Heart of Ice armor set.
Dragon Scale Armor:
Drake Scale: Piercing, Elemental, Toxin, Fire, Negative Cold and Electric, Damage Bonus vs. Slime and Gremlin Low.
Wyvern Scale: Piercing, Elemental, Toxin, Fire, Negative Cold and Electric, Damage Bonus vs. Slime and Gremlin Medium.
Dragon Scale: Piercing, Elemental, Toxin, Fire, Negative Cold and Electric, Damage Bonus vs. Slime and Gremlin High.
Dragon Scale Shields:
Drake Scale Shield: Piercing, Elemental, Toxin, Fire, Negative Cold and Electric, Damage Bonus vs. Construct Low.
Wyvern Scale Shield: Piercing, Elemental, Toxin, Fire, Negative Cold and Electric, Damage Bonus vs. Construct Medium.
Dragon Scale Shield: Piercing, Elemental, Toxin, Fire, Negative Cold and Electric, Damage Bonus vs. Construct High.
Silvermail Armor:
Add a helmet to both Silvermail and Radiant Silvermail.
Silvermail: Elemental, Shadow, Electric, Negative Fire and Cold, Damage Bonus vs. Undead and Construct Medium, Universal Attack Speed Low.
Radiant Silvermail: Elemental, Shadow, Electric, Negative Fire and Cold, Damage Bonus vs. Undead and Construct High, Universal Attack Speed Low.
Angelic Armor:
Angelic: Piercing, Shadow, Fire, Cold, Negative Toxin and Electric, Damage Bonus vs. Fiend Low.
Seraphic: Piercing, Shadow, Fire, Cold, Negative Toxin and Electric, Damage Bonus vs. Fiend Low.
Fallen: Piercing, Shadow, Fire, Negative Toxin, Cold and Electric, Damage Bonus vs. Undead and Fiend High.
Valkyrie: Piercing, Shadow, Cold, Negative Fire, Toxin and Electric, Damage Bonus vs. Beast and Fiend High.
Heavenly Iron: Elemental, Shadow, Electric, Fire, Negative Toxin, Cold and Curse, Damage Bonus vs. Construct High, Movement Speed Increased Low.
Chroma Armor:
Chroma: Normal, Piercing, Toxin, Fire, Damage Bonus vs. Slime and Beast Low.
Virulisk: Normal, Piercing, Toxin, Damage Bonus vs. Slime and Beast Medium.
Deadly Virulisk: Normal, Piercing, Toxin, Damage Bonus vs. Slime and Beast High.
Salamander: Normal, Piercing, Fire, Damage Bonus vs. Slime and Beast Medium.
Volcanic Salamander: Normal, Piercing, Fire, Damage Bonus vs. Slime and Beast High.
Arcane Salamander: Elemental, Piercing, Cold, Electric, Negative Toxin, Fire and Curse, Damage Bonus vs. Gremlin, Construct, Slime and Beast High.
Archilus:
I'm not exactly sure what I'm supposed to do with the Hooded armor sets. Clearly, I can't just turn all of them into Chaos sets, and these sets are already really good as they are. However, there are some things I can change to give them a bit more oomph.
Magic: Unchanged.
Elemental: Unchanged.
Miracle: Add Universal Damage Low.
Grey Feather: Add Negative Toxin and Cold; add Universal Damage Medium.
Divine: Change Shadow to Normal; change Fire and Shock to Negative; add Toxin and Cold; remove Curse; add Universal Damage Medium.
Chaos: Change Normal to Shadow.
Walkon:
Again, there isn't much you can do with this, especially when Slime armor has no sidegrades aside from a completely unrelated armor set. However, I'll include Quicksilver to make this make sense.
As with Zebulon's armor, I'll list the full stat profiles rather than just the changes.
Slime Armor:
Jelly: Normal, Piercing, Sleep, Stun, Negative Electric.
Brute Jelly: Normal, Piercing, Sleep, Stun, Negative Electric.
Rock Jelly: Normal, Piercing, Sleep, Stun, Negative Electric, Universal Charge Time Reduction Low.
Royal Jelly: Normal, Piercing, Sleep, Stun, Negative Electric, Universal Charge Time Reduction Medium.
Ice Queen: Normal, Piercing, Sleep, Cold, Negative Electric and Curse, Universal Charge Time Reduction Medium, Movement Speed Increased Low.
Quicksilver Armor:
Quicksilver: Normal, Piercing, Electric, Negative Stun.
Charged Quicksilver: Normal, Piercing, Electric, Negative Stun, Movement Speed Increased Low.
Mercurial: Normal, Piercing, Electric, Negative Stun, Movement Speed Increased Medium.
Slime Shields:
Rock Jelly Shield: Add Damage Bonus vs. Slime and Beast Low.
Royal Jelly Shield: Add Damage Bonus vs. Slime and Beast Medium.
Sylvin:
Skelly armor makes me wonder why it doesn't have a Damage Bonus vs. Undead, so it will get one.
Skelly Armor:
Skelly: Add Negative Stun.
Scary Skelly: Add Negative Stun; add Damage Bonus vs. Undead Low.
Sinister Skelly: Add Negative Stun; add Damage Bonus vs. Undead Medium.
Dread Skelly: Add Negative Stun; add Damage Bonus vs. Undead High.
Skelly Shields:
Sinister Skelly Shield: Add Negative Stun; add Universal Charge Time Reduction Low.
Dread Skelly Shield: Add Negative Stun; add Universal Charge Time Reduction Medium.