Some of the things I think would take it up a notch or two:
- Maybe more keyboard related stuff. I like the Shirt, Poster, and sticker, but i think extra keyboard related items would be cool too (sleeves, keycap pullers [if you could somehow incorporate special keycap pullers
)], etc)
-This is where things may get a little weird, but I think keeping caps limited to the CE would be cool. Adds and extra level of exclusivity, and makes it more "collector-y" (Side note: Maybe you don't have to keep just the main keycap limited to the CE, but maybe others would be limited, like this current CE, a neon green/black themed gamer set or other caps to go along with it, and only available with the set, not entirely sure how this would fair with other's opinions, but I like limited extras and limited main, but that's jut my two cents)
-I think the ~125 price is fair. Obviously the price would change if you're adding sleeves, other keys, or who knows what, but I think that price is very fair.
-Display case. Either for just the cap, or somehow for everything. This would add a bit to the price, but I think it would be super cool
-I saw some others mention limited edition key testers. I think that would be neat too
Overall, I think changing it up every time would be the most important thing. Don't just have a shirt, poster, and sticker with every single one. Keeping them similar is nice (something smaller like a sticker would be great in every one though, I just think that repeating the same "main" add-ons would be as attractive as changing it up each time), but variety is also what sets them apart. Thinking about game releases that come with collectors editions like these, three that come to my mind are the ones for Far Cry 4, Fallout 4, and GTA V. They all had very different things in each collectors edition, but all also contained a few of the same things (they all came with posters, but the larger items differed greatly).
One question though, will we see more compatibility with these in future CE's? I think it would be nice to have an option of mx or Torpe stems for the CE.