Being honest it's not bad that they've posted their ideas in a new thread. If the thread was a single one of these, yeah, I would say go necro one of the hundreds of other threads, but a compilation of ideas isn't too bad, even if all of them have been suggested before.

So I'm going to go ahead and smack your suggestion's hope and dreams around a bit, and we'll see where it ends up.

- - Two Handed Weapons and Dual Wielding - -
Going to come off strong here and say no. Shielding is much more than just blocking damage - it is the livelihood of almost all advanced weapon tactics. Dual wielding two weapons is a bad mechanic in the flow of this game - creating new weapons that use two hands is plausible however. The difference here would be that using two hands would not have any real gameplay effect over using one hand. You could still shield, charge attacks, etc... It might just be more of a troika situation. Cosmetics are always welcome.

Only problem here is you would need to create unique animations for these new weapons. I don't mean just for attacking either - shield bash, shielding itself, and the charge animation would need a new appearance. Not really bad, but just something that goes deeper than just "add weapons".

My personal thoughts on this is to make more unique shields. The shield would act as a weapon, such as countering attacks, deflecting bullets, or perhaps giving player-buffs (or have a percent chance to dodge an attack entirely rather than block the damage. Less reliable, but when it works, it's more effective). The more attributes we give shields, the more advanced shieldplay can become. With more advanced shieldplay, well, the need for two-handed weapons effectively drops to zero.

- - Axes and Hammers - -
Still hold true to my "two hands cosmetic" approach, so two-handed hammers and axes would still be a cosmetic appearance.

However, you see to see axes as a sort of throwable weapon? While this is a gun's job, I'm sure you could sneak throwing axes into the game through various ways, such as a 3-hit combo where the final attack is throwing the ax. However, the ax can act like a bomb, in that you throw it but it's still with you. If you wanted to throw your weapon like a boomerang that'd be more for a charge attack.

- - Lances and Spears - -
Here's one that's been suggested for a long time due to the extreme lack of piercing swords. Having "heavy" piercing swords would also allow for a nerf to the flourish's rather absurd range. Having these swords have extended range however be more single target instead of a wider area of effect would also fill an interesting niche.

I also want to make a gorgo kebab, and lances seem the most appropriate in that area.

So bottom line is two hands bad, unless cosmetic. More weapon ideas good, especially if they bring new styles of play to the table (axes/lances).

Just a correction: for so long we've been under the illusion that Three Rings doesn't implement dual-wielding because the shield is so crucial, and in a way that's correct. But there's a bigger reason why, that has been brought up on other highly skill-based action RPGs. (namely Secrets of Grindea, which has very similar combat mechanics to Spiral Knights) Dual Weilding isn't underpowered, it's actually overpowered, because obviously its implementation is "lose shield for more damage" or some variant thereoff, but we already do a lot of damage.

Dual Weilding would be like the weapon slot equivalant of Chaos Cloak.

Equip Chaos Cloak
Equip Dual Wield
Equip BTS
Nothing stands against you
Win game

There are already two too many broken weapons in the game, (Acheron, Blitz Needle) plus a plethora of not broken, but still overpowered ones. We don't need more.