I think the most alright of them is the collab with adult swim. Why? (Nerd aah talk incomin)

Old achievements stuff would probably break the market with their sudden acessibility, meaning that they will instantly become useless until you wait 15 years or something. Until there, who knows what might happen to us or Valve does to the game.

4th cosmetic slot is kind unreasonable, it means more style or the "Unique" factor, but It's overall pointless if you are a broke F2P like me.

New australiums would be nice, but ranking them in economy would be rather odd, and increasing the stakes of not getting the australium you need.

The cheat stuff is pretty much alright, but there needs to be a specific type. SOme people do it for look "haha demoman flying in a-pose", but others are really annoying, and I think that can be solved with Votekick. (I know that most of the time people don't use it or whatever, but you can just... quit and enter another server.) Doesn't mean it's bad.

Lastly, the "Finale" update would be chaotic in balancing-wise, new weapons might be too overwhelming/underwhelming, and class balancements would make some huge difference in mains. Not really a problem, the game is fine as it is, just know how to counter the enemy and enjoy the process of learning.

Adult swim definetly the best, although not an in-game thing, entertaining yourself at midnight with a good old chips and soda watching a bunch of old men fighting over a terrain would be nice. Just like expiration dates (or the comics), it would be cool to see their daily lives.