NOTE: I'll get around to sketching up some artwork so I can give you an idea of how I see this idea in my imagination, plus it gives you the opportunity to understand my ideas in a more solid and tangible way.

So I was reading through Mrgrey's thread named "Buff Cutters: Make them Worthwhile" in the Suggestions section and had this crazy-awesome idea!

The way I envision it is basically like an elaboration and expansion of the Lockdown shield mechanics/slots but for use in PvE (and maybe PvP?).

How cool would it be to have specialized shield type that could really add to the current model of combat? Let me explain.

To differentiate the "play styles" we need to further define them and carve them out to avoid succumbing to cookie cutter/common class archetypes.
I was thinking that Three Rings could develop and implement an entire new system for making shields far more diverse and interesting, bringing the shield slot up to the same level of importance as the weapon slots - meaning - instead of just looking at the stratum type and going "Oh, fiend-type stratum." *plop* [insert shield with Shadow defense here] "Done.", it means you actually have to think about what shield attachment/ability you're going to run with instead of the shield being a universal "Block" button that only delays your inevitable impending doom. My initial idea is that they would be slightly weaker shields but with a certain amount of charges or uses that activates the shield ability, but then I thought why not just add a new type of sub-slot for shields where the abilities can be used with existing shields?

I think a cooldown is in order for this idea, I just think if we get some really inventive, elaborate ideas for abilities, they're at risk of being OP, so it's a really simple and logical way to counter shield ability spam and make you properly think about the situation and whether you really want to expend a charge it because you once you've popped the cooldown, you've got - for example - 3 minutes before it recharges.

Staying true to the concept of diversity, there should be several types of shield specialization to choose from such as, Attack/Damage Buffs, Heavy Shields (revamped shield bubble with extra shield health maybe?), Smoke Bombs (disables enemy lock-on ability in the smoke-screened area?), AoE/party-wide Status Resistance Increase, spawnable/portable mini-arsenal? These are merely examples of a few possibilities, I'm sure there's some pretty creative minds out there that can come up with some fantastic options for shield abilities.

EDIT 1: Maybe the existing bosses and bosses to come could have mini-abilities or very distinct attacks that have a shield ability counterpart that players could use to counter the boss ability/attack. It would add a little more variety and rhythm to the usual "Bash-Bash" ,"Pew-Pew", "Charge-Boom" combat. I don't want this to become World of Warcraft where the bosses have a plethora of abilities to throw at you (on the other hand, if it were done right and kept fairly simple to suit the arcade style of Spiral Knights it'd make bosses far more challenging and rewarding to actually kill)

I will continue to update this as my idea of this expands and look forward your ideas and feedback.