I'd like to see levels put into the game where things like strong winds or water currents add a difficulty mechanic to doing things like navigating spikes or dodging enemies. Seeing as adding moving water seems like a lot more trouble than its worth, it would probably be unrealistic to suggest canals, rivers, etc. (Not to mention that adding things of that nature imply level design changes on a much larger scale, though I'd very much like to see more water incorporated into Spiral Knights level designs in general.)
On the other hand, a few large fans in Gremlin levels or perhaps just a bit of wind in the Wolver Dens (or Scarlet Fortress, you know, whatever.) wouldn't be too hard to implement at all.
Tier 3 Windy Arena. It'd be a blast.
I don't see the point of this other to annoy people when they get pushed onto spikes for the 10th time that run.