I always thought it would be interesting if status effects could be combined to get a different effect, and some to even cancel out.
Two other games come to mind which use this to satisfying effect, Warframe and Guild Wars 2.
In Spiral Knights, status effects work a bit differently, it would probably fall somewhere between those two games in how it works, especially since the status and element types are quite different than in those games.
To give some ideas of possible combos, here's a list, I'm sure you guys could think of more, unless you just decide to shoot this down: