Well, title says it all. I've had several ideas floating around in my head ever since I got back into the game. These are all Single Player focused - I don't play MP.
In addition I'll be listing my requests from what I believe to be the most to least feasible with the community's current knowledge of JJ2. Granted, I'm a newcomer so my own knowledge is lacking and based off of assumptions so I apologise if I come off as presumptuous.

First of all, a bug: completing a secret level usually sends you back to the original level's warp point, and said original level will be in the same state you left it in, taking into account what you collected/killed/triggered. But if the level ends with a boss fight you are sent back to the beginning of the level and the level state resets entirely with the only change being that the secret warp is no longer active. I am unable to check if it's Plus exclusive but I'm fairly certain it's always been like that.

Now, requests:
1. I'd like an option to disable the sugar rush music. It is considered a sound effect instead of a music file so turning the music down has no effect on it, making it very loud if you turn down music but keep the SEs.
2. An option to turn off the 99 ammo cap, thus allowing the player to collect additional ammo and as a result making it function more like it did in Jazz1 and OEM. Obviously SP only.
3. In the OEM versions the Queen would drop multiple cinder blocks on you if you play on hard mode. I'd like to see this feature restored for Hard and/or Turbo.
5. Don't know if this counts as a bug but completing a secret level resets your coin count in the original level back to 0, which is a problem if you already collected the level's coins before entering the secret level. Just like with the above bug I assume it's present in all versions but cannot verify it.
6. This request is perhaps the tallest order here by a huge margin: restore the original function of the gems as a way to gain extra lives. I don't know if this is even possible without access to the source code which is why it is at the bottom of the list. I literally only put this in the slim hope that against all odds this is actually remotely possible and I'm not actually expecting anyone here to try doing it.

So yeah, I don't really know how to end this so... Thanks in Advance!