New Weapon Types:
Bows - Long Range, Slow attack Speed, VERY high Damage. A mix between a gun's attack type and bomb's attack type in which, you can only charge it but it fires a strong projectile. They always inflict status. They can only hit one enemy at a time, but do very high damage. This is what you want if you want to play as a sniper.
Spears - Long Range, Slow attack Speed, Medium Damage. Just like the ones the Almirians use. Their range is almost as good as a gun. Their damage is slightly higher than a gun, however. Basically an alternative to the flourish.
Maces - Medium Attack Speed, Medium Damage, Short Range. They can inflict the stun status and a status unique to maces, crush which is basically Seraphynx's defense down status.
Flails - Medium-Long Range, Slow attack Speed, High Damage. An AOE weapon. attacking with this weapon throws the flail out in front of you. Which will stay on the ground. Each successive click moves the flail around allowing you to damage enemies. Your player movement also affects where the flail goes.
Unique Variants:
Specific Damage Bonus UVs can go beyond Maximum(6 stacks) All the way to Ultimate(9 stacks). So while a maximum damage bonus (full black kat set) may get 221 damage on a weapon fighting the undead. Someone with Damage bonus Ultimate against undead may get 255 damage at max rank, but against only undead. Would be a nice buff to all the weapons and armor out there that have these attributes.
Attack Speed Increase can now be rolled on bombs. It decreases the fuse-time of said bomb(the time it takes for it to ignite after placement).
Shields can now get Damage Bonus UVs and Recharge Speed UVs rolled on them. Damage bonus increasing your damage of the bash, and Recharge speed decreasing the time it takes for your shield to recharge after a hit.
Shields:
If you decide to unequip your shield because you're a dare devil you will actually gain some buffs. You will gain a Movement Speed Increase Medium due to the weight loss and a Attack Speed Increase Low to all your weapons. Your dash action's cool-down will also be reduced by 2 seconds. Allowing for some speedy but very risky gameplay. Would make for an interesting play-style. Right-Clicking will instead use your second weapon when your shield is unequiped. So it will kind of be like dual-wielding.
Shield-Bashing Changes:
Certain shields should recieve bonuses to their shield bash and some visual effects. Shields such as the blackened crest will inflict fire on hit foes in addition to the stun. Barbarous thorn shield will release thorns in the direction you bash, which do piercing damage. Lower-ranking shields such as SurgeBreaker, BlizzBreaker, and Blazebreak shield will all inflict strong shock, strong ice, and strong fire respectively on their bash. If a shield resists the damage type they're facing, they will do extra damage in their shield bash. Heavier shields Inflict stronger damage numbers and strong statuses, but reduce your shield capacity by more.
New Status:
Confusion: Can be inflicted on by heavy weapons and certain enemies can also inflict this status. When inflicted on a monster, it causes them to attack their allies. When inflicted on a player, it reverses your controls.
Set Bonuses:
Wearing full sets of a matching armor will net you some unique bonuses. Each armor set line will have something unique about it to keep players crafting Keep in mine these effects are for the highest star version of the armor. Lower ranking armors will have a WEAKER version of said set bonus. Here a few Ideas I had:
Jelly Armor Line: Slimey:
Grants a Slime to fight with you, just like the one from the Golden Slime Casino.
BlazeBreak Armor, SurgeBreak Armor, and BlizzBreak Armor: Inferno, Storm, and Blizzard:
Grant a status mist aura around the player which has a small chance to inflict said status on an enemy.
QuickSilver and Mercurial Demo Set Line: Sporadic:
When Shocked, you gain Movement Speed Increase Maximum and Attack Speed Increase High
DreadSkelly Line: Calling of the Undead:
You gain an extra free revive.
Wolver and Skolver Line: Roar of the Wild:
Gain a temporary attack buff when damaged.
Demo Line: Boom!
Bombs deal extra damage(stacks past damage bonus UVs).
Vog Cub: Fire Walker:
Leave behind a trail of fire which damages and burns enemies
Snarbolax: Roar of the Snarbolax:
Gain a temporary defense buff when damaged.
Kat Claw: Art of Claw:
Allies near you gain attack buff
Kat Eye: Art of Eye:
Allies near you gain attack speed buff
Kat Hiss: Art of Hiss:
Allie near you gain defense buff
Black Kat: Cursed!:
When hit, small chance to inflict curse on the enemy.
Virulisk: You are a true alchemist:
Vials will have double radius and longer durations when you use them.
Volcanic Salamander: Volcanic:
Imbues you and your allies weapons with the power of fire. Moderate chance to do Moderate fire.
Cobalt Line: Art of the Knight:
Your swords deal extra damage(stacks past damage bonus UVs).
Set Bonuses aren't meant to make or break an armor set. Only to make them more fun and viable late-game.
Just spilling all of my ideas into this post.
Oh boy, don't take this too harshly as I'm fairly critical on these sorts of suggestions, but I try to give my thoughts from my interpretation of the game's design, which I follow closely. For reference, the primary design decision that we will be using is "No Orcs, No Elves, No Goblins" - which translates to "do things differently".
New Weapon Types
I've seen many suggestions for new weapon types, but the largest question I always ask is "what do these do that we can't just have our current weapons do?". Bows, mechanically, are gun charge attacks. Spears, maces, and flails are all mechanically swords. There's no reason we can't have a sword do the things the spears, maces, and flails do.
We currently have a better version of a bow with magnus lines or catalyzer lines. They are guns that are heavily charge focused, but they are still a gun. Using this sort of unique approach to weapons and mechanics is critical, and making them simple enough to use yet hard to master is a wonderful way to design weapons.
New and Improved Unique Variants
Increased damage bonus caps for family damage would be very good. However, in wake of this, I would recommend making universal damage boosts lower, class damage boosts higher, or family damage bonuses higher on gear. I wouldn't recommend all three, but valkyrie should be the best fiend killer, dragon scale should be the best beast killer, etc.
Bomb Fuse Time would be cool, but I'd prefer it be its own unique stat instead of being based on ASI. This prevents the swiftstrike from being a bomber shield, and would open up the opportunity for some FTR weapons, armors, or shields to exist.
Shield UVs need a revamp for sure, but I'm iffy on these two. I'd need to see them in action before I can make a valid assessment of them.
Shield Bash Change
I've seen this suggestion a few times. It would actually be literally useless for shields to inflict the status that they resist since, if you are using the shield properly as a shield, the bash status will have zero use. If you aren't using the shield as a shield, then you're probably using a swiftstrike buckler anyways.
My recommendation would be to have various "shield bash" tiers, in which the shield trades shield health for certain utilities. For example, plate shields may have higher knockback and stun length on their shield bash but it does less damage and takes up 66% of your shield health, still requiring a full shield. Meanwhile the defender line of shields would have the current shield bash strengths but only eat up 33% of your shield health, perhaps even be usable at any amount of shield health.
While balancing these, keep in mind that status is not a good thing to put on shields, other than stun. No monster families are immune to stun (while certain slimes are immune to minor stun), but a freeze shield bash on a freeze shield will be useless against the freeze enemies that you're using the freeze shield to defend against. Knockback, shield health, potential damage resistance or immunity, etc will be better for this sort of system.
Confusion Status
I'm indifferent to this. It's not a bad idea but I'd want to see it in action before I make any large judgments on it.
Set Bonuses
I've played with this idea time and time again. On one hand, it's good because it makes full sets stronger. On the other hand, mixing and matching gear sets is a crucial design element for Spiral Knights, and set bonuses directly go against this. Armors and helmets could have lessened effects when only one piece is worn, but the bonuses need to have a fine balance and likely should pull from a handful of different options without getting too crazy.
Personally, I'm against set bonuses, but am instead totally for shield classes as unique behaviors on shields could easily fill in the power gap that armors leave in combat.