Note: I did copy my suggestion from this topic:
https://forums.spiralknights.com/de/node/121188
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One old suggestion that did float around for along time would be fallowing:

. . . Player Created Levels

By allowing players to create a level and publish it for testing, other players could rate this up. The highest rated levels will then undergo a check from Grey Heavens. If approved, then this Specific level would make it inside a Special Player-made-Levels-Gate where we only encounter levels that have been created by players.

To avoid obvious abuse and exploits, nobody will be able to gain any heat or coins or materials during testing levels. Those final levels that made it inside the special Gate will drop crowns and heat normally of course.

. . . Additional suggestion: Voting for a player's level will requie a very small amount of Moon- and Valestone.

Technically, Greay Heaven would need to implement a Level Editor or a program that allows us to do this outside of the game.

I do know that Grey Heaven's previous answer included the issue of randomly generated level pieces that differ from a whole static level setup. But even for this problem there is a solution!

A certain other game (Trove) allows the generation of player made dungeons inside a voxel world. A player firstly has to create a dungeon with a different program. Inside this program he can add different jigsaw pieces and mark specific points where one piece can connect to another.

Example:
So lets say a dungeon has one entrance A, a middle layer B and one Boss room C.
Then a player could make only one jigsaw piece A for the entrance and one jigsaw piece C for the boss room, but multiple jigsaw pieces B that can all connect A and C.

In the end there could be
-jigsaw piece A
-jigsaw piece B-1
-jigsaw piece B-2
-jigsaw piece B-3
-jigsaw piece C

The player needs to add certain key points that determine where exactly piece A will hit one of the B pieces and vice versa. And of course the same interaction between all B pieces and the C piece.

Going back to Spiral Knights, it could look like this:
We can create multiple jigsaw pieces and add connection tiles on the pathes where players can exit this specific jigsaw piece. We also would need to make a checkbox if a jigsaw piece needs to have another jigsaw piece before that will provide a key.

Furthermore it needs to be categorized so that a certain piece only appears around other pieces. Or in other words: we dont want a frost wolver grass tile aside a fire devility town tile (do we?)

For referance, this a video of someone making and explaining things with that other game:
https://www.youtube.com/watch?v=Ci1NqD63U9g
and here also a longer video of another guy:
https://www.youtube.com/watch?v=zAitcmSzMSQ