So, right now in Spiral Knights, we have trinkets for damage resistance, status resistance, and every aspect regarding weapons. However, what about speed movement? Now, I know people will say that the Mercurial Sets were designed for this purpose, but they don't seem to make much of an impact in-game. This trinket could help the set and make it go to Maximum! It would be the only way to get maximum speed, to mix the set with the trinkets. I say that there should be a trinket that increases speed of the player, at the expense of not being able to use another trinket for stats in other areas. This would work just like any other ability with Low and (possibly) Medium. It would become a Krogmo Machine module with a boot icon. Of course, this module could help armors that lower speed, for PvE, if you feel like it goes too slow for your pace. For PvP, in particular Lockdown. Let me explain:
Striker: This is, obviously, the fastest class in Lockdown. With the Speed Module, they'll go even faster, but who knows? It could be too fast for them, but if they decide to use it, it's at the expense of a ASI (excluding bombs), CTR, Damage, or Health trinket. This means that they would be speedy for capturing points, but they won't be the powerhouses that they are now (with the usual DA, GF, FF, BTT, etc.)
Guardian: This is the slowest class in Lockdown. With the Speed Module, they'll go faster, making them a bit more effective. Aside from being a powerhouse, they'll finally have some speed to counter the endless number of strikers. This class will benefit most because it is the slowest and will be able to become more effective in combat and defending points.
Recon: This, is the middle class in Lockdown in terms of speed. With the Speed Module, there could be a difference depending on its use. A Recon with their cloak up is more effective than anything. If they have the Speed Module equipped, they could go farther while cloaked and sneak up on unprepared foes.
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For Weapons (added because of Gingermace's comment on bombs)
Sword: This will help people who want to be like ninjas and go in fast, strike fast, and get out. Of course, it wouldn't help swordsmen as much as others, but swordsmen have a full set of trinkets to pick from otherwise.
Gun: The speed boost could help gunners dodge, because they aren't set for close combat usually.
Bombs: This trinket would help bombers in particular, as mentioned by Gingermace. It will allow bombers to get in the action, bomb ready, and then get out as the bomb "goes off". It takes the place of ASI and could definitely help bombers, which usually suffer worst in Lockdown.
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The thought of limiting the amount of equipped Agility Modules has been discussed. For now, it's up to debate until people come to a conclusion or one seems more convincing/fair/right.
tl;dr: A speed boosting module from the krogmo machine
There would be Agility Module and Elite Agility Module.
It could work for PVE for those slow armor sets. But it would be a small bonus and just one trinket in my opinion, so the balance wouldn't break. Because if there were 1 star-5 star ranked modules, that would break the balance of both games. So just one trinket and one boost related to speed.