First off, welcome. This is my first time making a Suggestion, but don't be afraid to give harsh criticism, as long as it's actually constructive and not just 'NU U WRONG THING SHOULD STAY THE WAY THEY ARE CUZ I LIKE BEING A CLONE STRIKER THAT DOMINATES LD' wrapped up to look like criticism, or 'THIS SUCKZ I DUN LIKE THIS GAME' covered by big sciencey words. :P
Second off, this isn't going to be looking at the weapons that could be considered 'OP', or at last not yet. This is simply a study and eventually a suggestion of how LD balances out and how it can be made more balanced, mainly through adjusting the classes. It's also a suggestion of other PvP options, so that we have more games to go two instead of just LD and BN.
Third, watch out. If you're a TL;DR type of person, you may want to just jump to the bottom where I'm going to summarize everything. However, if you do so and make a post, note that within so that I can point out something you may have missed by just jumping to the end.
Alright, here we go.

Let's begin with the Lockdown Balancing part, opening with a quick run-down of each class, the bonuses and penalties attached to each modifier and the abilities as well.

Strike Booster:
-3 Health (2 Base)
+Sword ASI Medium
+Sword DMG Medium
-Bomb CTI V. High
Shield button becomes instead a limited sprint button, sending you off at high speeds for 3 seconds per full boost.

Guardian Shield:
+Sword ASI Low
+Bomb CTR Low
-Gun ASD Low
Shield becomes gigantic, can slowly heal knights at 1/2 a pip per second or so and can protect all allies within shield. (It's classified as a status with a countdown timer of 1, being constantly replenished while the shield remains up and knights remain inside)

Recon Cloak:
+CTR Medium
+Gun ASI Medium
+Bomb CTR Medium
-Sword ASD Low
Shield is replaced by invisibility and deathmark 'radar', able to remove all defenses for 5 seconds after Recon and then Death Marked. (Can currently only sustain 1 hit while cloaked, that will change to more in an upcoming update)

So there. Stats for each class modifier. We can already start sorting them into the typical weapon classes: Swords, Handguns, and Bombs.
Each class seems to be designed for two weapons and discourages the 3rd, but does that really hold up?
Well, let's start with the obvious. Striker & Swords. Alright, so that leaves Recon and Guardian with Handguns and Bombs. We'll put Recons with Handguns because they actually don't have a negative bonus against it, and so Bombs and Guardian go together.
Simple enough, until you go at it again.
This time let's put Recon with Bombs, as they have both a specific CTR bonus and a universal CTR bonus for bombs, making it twice as effective. Strikers take Swords again, and--wait, what?
We're putting Handguns with the one class that has a NEGATIVE bonus for them?
What's going on here?
The answer lies in the bonuses, mainly of the Striker. Why? It's simple: Strikers have TWO specific bonuses for ONE weapon type, while Recon and Guardian have TWO specific bonuses for TWO weapon types.
It's a simple fix as well:
Change the Sword DMG bonus to a Gun DMG bonus.
Yes, there'd be uprisings. Yes, every clone in Dusker/Skolver gear will shout in anger.
But it'd be more balanced. As of now Gunslingers are getting the short end of the stick for LD class bonuses, and this small change would fix things, even if it's just a little.
And also, this would promote wearing trinkets other than Health Trinkets in LD.

There's another change for the Striker that could be considered both a buff and a nerf, at the same time. Instead of having the flat -3 Health penalty across the tiers, I'd like to make it so that it's -1 in t1, -3 in t2, and -5 in t3.
Before you outcry again, let's look at the reasons.
In t1, a Striker w/o Heart Trinks has a pitiful 4 health at best. That same Striker in t2 with 3* full heat gear? 8. t3, full heat 5*? 12.
With my system in place the t1 Striker would have 6 Health, t2 still at 8, but t3 now at 10 health.
{Fun Fact: I was pondering on whether to just have the Boost negate either Helmet or Armor Health bonuses, but decided against it due to those who use lower-starred gear/above average health-giving gear getting an unfair (dis)avantage.}

The other changes I have in mind are all for the Guardian. Yep, we're here again.
I'll be blunt: I could go ahead and rant on about the actual shield health and mechanics, but we've got that over here: http://forums.spiralknights.com/en/node/60167
No, what we're going to discuss is how the Guardian Shield scales currently, and how I feel it should scale.
Currently, all the Shield gains is more defense and health per tier. It's other ability, minor healing of 1/2 a pip, is unchanged.
This means, as a Guardian,
t1: You can heal to full health (fully heated 1* gear, no trinks) from 1/2 a pip in about 13 iterations of the healing 'status'.
By t2, with fully heated 3* gear, that increases to 21 iterations.
And in t3, full heat 5*, 29 iterations.
If we'd like to keep things at an equal pace, I'd say around the t1 1/2->full health rate, we're going to need to buff the amount per 'tick' of healing.
Hmm... perhaps 3/4th a pip for t2?.. That'd be... Aha! 13 iterations, and even with 1/4 a pip left over!
t3, full pip? Erm... Dang, that only evens out to 15 iterations for full health. Still, that's much better than 29.

Lastly for the Guardian, I'd like to increase his Sword ASI and Bomb CTR to medium. It'd put the nail in the coffin for a true balance of classes.

--TL;DR SECTION--
So, quick review for the changes made to each class:

RECON: Unchanged, fine as is.
STRIKER: Sword DMG -> Gun DMG, Health Decrease scales by tier: t1=-1, t2=-3, t3=-5.
GUARDIAN: Sword ASI Low -> Medium, Bomb CTR Low -> Medium, Shield has scaled healing: t1: 1/2 pip per tick, t2: 3/4 pip per tick, t3: 1 pip per tick.

--END LOCKDOWN ANALYSIS--

--BEGIN NEW PVP EVENTS SUGGESTIONS--

Alright, we're onto the completely new content! :D
So, to put it simply, I've been interested in giving swords and guns a separate game of their own, like bombs did with BN.
So, first up is the sword-only game!

KNOCKBACK BRAWL
Players are equipped with but a color-coded Calibur and put in various arenas, all of which are lined by spikes, fire traps, or the like. As in BN, players only have 3 bars of health--but here's the important thing.
The Caliburs deal 0 damage, and can only knock a knight back.
The aim of the game is obviously to knock opponents into the spikes, causing them to die. Points are gained much like BN, with the living players getting points when others fall. In-game dialog is the same as well, with 'Example-Knight killed Other-Guy!', 'Example-Knight had a death wish!', and 'Example-Knight killed teammate Other-Knight!'. By this, you can infer that friendly fire is indeed very possible.
Charge attacks are as slow as an unheated Calibur's, with the knockback not being at great as on the actual weapon. However, they hold great risk/reward power as the knockback is still quite high.
Power-Ups could include things such as Speed Up, Increase Knockback, Increase KB resist, CTR, and possibly even weapon modifier, where your Calibur changes into another weapon type, such as Cutter or Troika.

Onwards to Handguns!

SHOOTOUT
As with Knockback Brawl and Blast Network, player's gear is disabled in favor of 3-pip health and a color-coded Blaster. You're put in a simple enclosed structure, full wall on one side with low walls for the other four. (Can shoot over, but cannot walk past.) {Some arenas may forgo this for just one long bunker with every one in it}
To either the right or left of you will be the other team/people if it's that type of arena, and on all sides are various hazards, like rockets, or lasers and switches, etc.
Your goal is to survive, simply enough. Friendly fire is once more possible, but if you don't focus on the hazards you're going to have a hard time. You need to be able to take down both the hazards and the other players. Every death counts as a point for everyone alive, after all.
Same messages as BN and KbB, with the 'XXXXX had a death wish', etc..
Power-Ups could include Range Up, Speed Up, DMG Up, and possibly weapon modifier, same as KbB.

Fhew.

TL;DR:
Knockback Brawl: Use rainbow Caliburs to hit other knights into traps.
Shootout: Snipe other players while managing rockets, lasers w/ switches, and the like with only a Blaster.

--END NEW PVP EVENTS SUGGESTIONS--

Edit1: Removed references to health bonuses on Recon and Guardian, as they do not exist. Added Striker health decrease scaling.

Comments and criticism would be appreciated!