I've been playing Spiral Knights since the Steam launch and I've had many random ideas throughout that time. Some would probably be good ideas, most are probably silly, but there's really only one thing I can say would really improve this game for me.

Spiral Knights needs global servers.

This is a game that imposes no limits on a player's capabilities beyond their own skill, which is excellent, but the more I play and the better I get I see more and more cases where the outcome was decided more by my latency than my skill, which is not excellent. Fiend levels in particular require jedi reflexes sometimes - devilite attacks can be launched before the devilite starts to prepare the attack on my screen. Guessing what is about to happen is not good gameplay. No amount of content updates can make up for this.

Obviously I don't know how many players there are outside the USA, but knowing that I at least am being handicapped by nothing more than my physical location causes me no end of grief.

I know that this is certainly the most expensive suggestion that can be made (apart from idiotic threads demanding the removal of energy), but in terms of gameplay improvement it would do the job of every content update you'll ever make.