It strikes me as odd, that all of our events are targeted at high leveled players when the majority of players seem to be tier 2.
Tortodrones, black kats, Apocrea, these aren't things that anyone less than a veteran knight can feasibly do. The only events I can see being done by tier 2 players reliably are the annual events at Halloween, Winterfest and the Anniversary, and those come much less often and offer temporary rewards that newer players shouldn't really care much for, like costumes and things of that nature.
So I've designed two plausible events as examples of what could be made without much effort or coding experience, primarily as an example.
Crafting Frenzy
Event description: The Spiral Order has teamed up with King Krogmo (and his devilites...) to aid all knights with their crafting endeavors! Enjoy boosted drop rates in treasure boxes and more friendly unique variant rates when crafting!
Rate changes for drops in boxes: around 1.25 x odds for all rarities, around 2.5 x odds of getting gear drops
Rate changes for crafting UVs: 3x odds of getting some UV when crafting gear
New daily mission: Hunt for treasure!
Description: The spiral order is providing free elevator passes to a collection of profitable levels in tier 2!
Level rotation: (starts at depth 10, goes to depth 14, playable once per day for ~2 weeks)
Level 1 = Compounds, with spiral order + krogmo's devilites explaining this is as close as they can go due to interference.
Level 2 = Treasure vault rotation = compounds/decon zone/graveyard/treasure vault
Level 3 = Treasure vault rotation = decon zone/arena/graveyard/treasure vault
Level 4 = Treasure vault rotation = clockwork tunnels/arena/graveyard/treasure vault
Level 5 = Treasure vault rotation = treasure vault/arena/arena/graveyard
Slime Invasion
The big new enemy: Explosive Slime
Description: Behaves like a walking explosive block
See "explosive block": http://wiki.spiralknights.com/Exploration#Explosive_Blocks
AI: Same as normal slime cubes
Health: Think bombie, but doesn't explode on purpose.
The event: Slimes have gathered forces with help from devilites and invaded all levels of the clockworks!
On most monster spawns, for all levels: 35% chance of becoming a normal slime cube
On slime spawn: 40% chance of becoming an explosive slime
Rewards: During the event, all slime family monsters give 25% more crowns. Explosive slimes have a miniscule (think margrel) chance of dropping something new and interesting, like say.. a node slime themed swiftstrike buckler that grants ctr med instead of asi high.
Note: This could be done with just about any monster type, and doesn't even need to have a new enemy if coding it is too difficult.
So basically tier 1 Blast Cubes without a timer?