The concept for this is fairly simple... at the end of a stratum, there's a chance that the final level, if it's randomly generated, will spawn a miniboss room at the end (as an attachment that bridges what would be the last room of the level to the elevator).
In the case of compounds, the arena would replace the battle area in the end.
I'm flexible on the details of how these spawn. These could be optional, and have the boss drop prize box items upon defeat. Or they could be required to continue. Either way, these are more or less edited versions of existing enemies; they're made specifically to be (relatively) simple to program while still being a half-decent challenge for players. For the most part, the arenas are all about the same size and shape (comparable to Snarbolax's arena, maybe a little bigger).
Now, I'm certain that I'm not the first person to dream this kind of thing up, but with enough pressure from peers I ultimately decided it would be worth sharing.
Descriptions of each boss are in this link: https://docs.google.com/document/d/1waaqYHuz7evc8z9vzySUdqxAPAQ08IX6hBgA... <
Be aware that nothing on the document is set in stone, and I may change it as suggestions come.
Judging from the new Arcade boss ideas, I'll say that you want GH to add in more new bosses to the Arcade.
Well, while I admire the details from the document you made, and am aware nothing in that is set in stone, even if I can't see the images of said concept bosses, there are some things to know...
1.) Implementing a new boss takes some time, and it's not just the concepts to make, there's some programming, coding, refining, modeling and animating, prototyping & testing, & so on to do before it's properly ready to be in SK. You'd have to be fluent in any of said steps besides concepts to bring said boss ideas to reality. Takes practice if you want to do these. Plus, there's learning of SK's polygon counts, texture sizes & particles to do, and know how they have their set limitations to adhere to them.
2.) The Freeze-themed Wooly Snarbolax, Battlepod boss(which already has one who has the exact name, E.G., Grinchlin Assault) & Ironwood Sentinel(there already is one, a miniboss in the Tutorial's end, thank you very much), I think they'd be better off being arena bosses towards the King Krogmo Boss Brawl Arena suggestion that I came up with, with Battlepod and Ironwood Sentinel needing different names & appearances to distance them from the existing ones. Takes more than coming up with a duplicate boss that already exists. Plenty more.
3.) If you wish them to be in the Arcade, main boss, or miniboss, or even both at once(could be possible), they'd need new level stratums of their own. Of course, it'd take time to squeeze in a new level stratum in the Arcade's randomized stratum roster. And even with that, there'd have to be a new set of Rank Missions to go with it, which would take effort to squeeze them in-between current missions.
4.) Grey Havens are only a small company. They're still busy with other things to keep people happy. Even if they would like to add in new bosses, they will still need time to implement them in. If GH decides to have more people to help with everything they have, volunteer and/or career-wise, preparations are necessary for such needs.
I still admire the creativity you're putting into your suggestions, but there's some more learning to do. Ask anyone who's more fluent in said steps to learn more info.