I'd love to see all the above with maybe a couple of extras:
1. Volume levelling revisited with no detriment to sound quality, which I believe was an early complaint of the method employed to achieve this.
2. Being able to swim in an artist (on C15 - don't know about the rest) from the album view instead of having to go back to the explorer view to get the option.
3. When shuffling a playlist, that the original playlist order is not then overwritten.
4. To be able to re-sort playlists at will between a host of options like date added, date recorded, number of plays, artist, album, genre etc etc.
5. To have C15 and iPad versions identical in look and functionality (including the full sweet of editing functions being available). I love to tinker and housekeep my collection and would much prefer doing it from the iPad while listening to my music.
6. To also have the web client look identical to the C15 - so I can use my Surface 2 as a C15 - or bring out a dedicated windows app that accounts for the widescreen presentation of the majority of windows tablets(compatible with windows RT of course).
7. Allow the user to specify full caching of the album art on the iPad for those that get an iPad just as an ultimate remote and are not worried amount filling the memory.
8. Allowing the iPad as a local zone and having multichannel support - thought I'd throw those in again for good measure.
9. How about 4K 3D video and Atmos support

That's me done for now. Thanks again Enno for keeping in touch.