In order to spice up the Arcade, here's a very simple, easy to throw together way to assemble content while trying to keep the raging playerbase content.

Create Danger Rooms involving bigger and badder enemies, like a reskin of the Collector! It wouldn't be too hard to adjust its damage and defense values for each tier, and I'm sure there are some people who would more than appreciate being able to fight a Tier 3 Collector in such a way that it doesn't end in a single Brandish charge. This could also be a way to bring back the Jelly Green Giant, Vog Cubs, or some other special monsters that have otherwise been dummied out. And the best part? The resources are already there. Just slap together a new setpiece, throw in some kind of 'difficult' monster, and bam!

"New" Danger Rooms!

But what about lore? Well, that's simple. Worry about it later, just as usual.