Not the one you quoted, but for me it's little niches such as the ability to sort e.g. by albums (folder skip is not the same thing, you can't use shuffle to jump to another random album), to use other file system or to
choose the typeface. UX-wise multi-press like what done in
Sxmo could also allow changing playlist ordering mode or toggling button lock.
None of these is particularly difficult to support in theory, but the licensing nature of MTouch OS does not allow one to patch it, and constantly nudging Shanling for certain features is not exactly pleasant for either side. It'd be best if they can release the OS as FOSS, plus the future maintainability when (hypothetically) the company decides to stop supporting the device or go under.