Firstly, please do not post DLC as we all want more!
If you could improve the game engine from what it currently is to do something better and/or fix an existing problem/bug, then what would those things be?
For me, I have a small list
1) Fix the switching between bass+guitar scores in quickplay (GH:WT PS3)
2) Have scores per difficulty in quickplay. So you press left/right on d-pad to move down/up the difficulty levels that you have from easy-expert, these are your local scores. The last score would show the highest achieved and level, which is the one that is sent to the leaderboards and is also the default one you see.
3) When playing a song it automatically selects the play level based on your solo high score for offline and online play. It gives a nice indication at what level you can do on this song.
4) An option to have auto-kick pedal for drums with either no score recording or a new type of score recording. The reason for this is that people with leg disabilities can still play (I pulled a muscle in my leg and was unable to play drums for a week!) and it helps when you have friends round who hate Easy because it is slow but also hate the pedal.
5) Bug-fix the text, "Congratulations, You are #1 on your friends list!" which shows when you play but do not beat your score when you are already #1 on your friends list. When you get a score just underneath your best when #1 then it should say something like "You did not beat your previous score. You are still ranked #1", or similar.
6) Use a slightly different shape which indicates that it is a cymbal and not a drum for those who have the cymbal add-ons. Sometimes my brain gets confused and I hit green cymbal instead of green drum
I post the above as someone who has progressed from Easy drums to Expert drums (on almost all songs) and what I would have found helpful during that learning curve.
Oh, and the biggest thing I love about the game engine is being able to see friends scores on quickplay so I can see how badly I am doing
So how would everyone else improve the game engine from what it is?