It's on my never ending todo list (I even tried to crowd source this on the Winamp forums a decade ago & people didn't care) but I need to replace more parts to be less encumbered by Winamp core functionality & also to have the main plug-in formats be able to support it directly (e.g. in_mp3 still needs to see a replacement started).
As any Winamp plug-in cue solution at the moment is a hack (assuming it's one of the ones that still works) & I want to do it right i.e. starting playback can cause some audio issues in some cases since it's got to start playback & pause it quickly before seeking to the desired position & then resuming playback. Also if you're just playing a file+cue through in order then other than the visual aspects there's no reason for it to be closed & re-opened which can cause track transition blips.
-dro