After this update came, some of us old folks who remember the sloom from the beta also remember two things you removed

First up:
http://forums.spiralknights.com/en/node/1006#comment-6337

From Poseidon:
I think I know which one you mean. We used to have Giant Green Jellys in there, but since that floor was on the Sparrow Gate or the Firefly gate we realized those monsters would tear the poor new knights to pieces. So it's on the to do list for some new inhabitants before it's opened up again.

It was removed in 2011, prior to the Battle Sprite update, the Gunner Update, the Devilites nerf and the Wolver nerf. We became so strong nothing can surpass us now.

We need a challenge and this is why I'm asking on behalf of all my veteran friends who can solo each Shadow Lair prior to the BS update without problem.

BRING BACK THE JELLY GREEN GIANT AND GOLDEN MOBS

The Arcade is the perfect place for this kind of stuff and with all the buffs we got throughout the years I think it would be really fitting to finally have a challenge.

Second part:
Yes, I am aware that some people still struggle with the game but getting to FSC from the Arcade would trigger Golden Trojan to appear in some places (D24 in the statue arena, D25 in the tourniquet from wave 1, D26 at start, D27 in the wolver arena and two on 3rd phase of vana and forward). They def should appear in Shadow Lairs too.