I have been playing this game since around a year or two after it first came out (on and off). This game is awesome, but it gets boring and repetitive to those who aren't addicted to seeing progress, but instead are excited by more action packed, fast paced games. So why not make game mechanics that really call those people in? Think about it, new content won't make people want to play, nor will making the game pretty. If the game is fun and has endless possibilities to fool around with, A serious PVE side in the end game, and a PVP so attractive it will look fun even when compared with MOBAs, why wouldn't many different styles of gamer flock in? SO I believe if you made the core mechanics more versatility calling for limitless possibles it would be much more fun. It is easy to say this, but hard to execute I have a few ideas here and there and maybe other people can input as well to make it easier and more balanced.

Spiral Knights combat system is outdated TO BE HONEST and we should welcome newer more versatile ideas

-Tanking Options: Half Circle shields bigger than that of the normal shields and works the exact same as a normal shield, but could protect more than just the user from a lot amounts of bullets and Sword swings, BUT your offensive capabilities would have to suffer + you will not be very immobile. Maybe it could also increase size so that it is clear you are the front line. ( You will revert back in haven, but on the battle field that is where these are visible)
Damage Reductions that actually save you from being eaten alive or armor pipes that overlap your normal pipes
Less Clunky shield bash
Maybe a dash that builds up speed making these guys look like really cool juggernauts.

- Offensive Options: Unique and versatile charge attacks
*Note I would say they did very good on all the different slashing styles and projectile styles
Making the useless weapons like the Windmillion, Wrench wand, and Starting game weapons like the Slime shovel and Beast hammer become a special type of utility weapons.
Also Dual Wielding would be a nice idea that could add some serious team play in the late game instead of HIT IT AS HARD AS POSSIBLE or carry Weapon (X, Y and Z) to make sure you will have an easy time in this level. (To eliminate a very strict meta)

Depending on your SIDE ARM or maybe they can keep shield and give attachments called modules (Your Knight will look different and act different)

Sword sidearm (swiftness mod): Draining shield bar for maybe a speed boost
Gun sidearm (Agility mod) : Gives you that dodge that is there (on shield shift I think). multiple depending on your gun or maybe movement ( More speed = More jumps) (More Speed equal shorter more frequent jumps Less speed equals Longer less Frequent jumps) (Sub-mech user are normally really fast and agile while snipers are kinda slow and patient waiting for the correct condition to strike)
*Note: instead of having that jump on shift shield it can be change into a tumble that everyone "class" can use, but the Animation time would be change depending on the speed of your character.
Normal shield (Push mod): Works like the average shield (With the push)
Heavy Shield (Guardian Mod): Works like the half shield I described

I feel like a game mechanic update would be 100% the right way to go and I hope someone's idea gets taken into consideration. (Also so if it looks like it is all over the place this is the reason why I normally fail English xDDDD)