There are advantages and disadvantages to using the N800 as a primary music player compared to - say - an iPod. I'll have to hammer out an article in the very near future on this topic.

I think my biggest annoyance was keeping SD cards separate and then having to re-index them when they got into the device. I resolved this by putting all video on one card and all music on the other.

The features you requested are very specific and rare - I don't expect them to come from a single music playback program in the near future. The N800 is better as a desktop/office/car portable media player and not a pocket device specifically because touch controls cannot be used intuitively while within the pocket. Thanks for the inspiration - I'll get to work on this article.