Awesome post! Going to go through it point by point.
1. Totally agree with you. I gave up trying to hit the target and long touch instead to get to the context menu. I'd say this was a bug but spotify would probably consider it a feature so can I suggest you start a new idea on this?
2. Swiping up used to be a feature on iOS but it was removed, I think, because it interfered with iOS 7. I'll disagree with you here - touching the bottom bar needs less effort than swiping up.
3. Rearranging playlists has been requested. Please add your support. I'm not sure how useful being able to drag music around on a small screen device would really be. I had a quick scan through the ideas section and don't see anything relating specifically to android so maybe post a new idea there requesting that the standard drag feature be enabled in all views?
4. A lot of android apps use the soft menu to avoid cluttering up the screen. However, it would be more intuitive for seach to be listed when I touch the android soft menu button too.
5. I don't agree with your assumption here but you can filter on offline content only already. Slide down in most views to reveal the filters one of which is "offline content only". Intelligent autoswitching would be nice though - post a new idea. I'll vote for it 🙂
6. This is fine for users with newer devices with 32 or 64GB of storage and an external SD card but what about users with older, budget devices?
7. This looks like repetition?
Overall I agree that it would be an easier user experience if the app rigidly followed Gogle's guidelines but I think we need to remember that the app also has to perform on older devices running android 2.2 and the overall look of the app is important too. I sometimes use the samsung music app and playerpro and, to be honest, I find those interfaces totally intimidating in comparison.