So on reading through things, it's basically a fullscreen now playing view with basic player controls and related information to what's playing (assuming there is the information there to begin with).
Straight up I'll say that I have a number of issues with MiniLyrics and how it works & integrates with Winamp (which I've never found to be all that good though maybe it's improved since I last tried it out - were placement, skinning and loading issues that I remember which didn't make for a nice experience).
My initial thought is that it could just be done via an embedded web page and hook the HTML5 player controls but I'm not sure how well that'd work with the IE based webbrowser control that Winamp relies upon for such things. If anything, doing it more 'natively' might be the better option and some aspects aren't too far off the bottom part of
https://winampplugins.co.uk/gen_classicart/gen_classicart.png from the album art plug-in for classic skins.
And for the final thing about embedding lyrics into files directly, MiniLyrics possibly has the option but for Winamp itself, it would need changes to the native input plug-ins that handle all of those things or (as I'm planning to do) replace that handling with a centralised tag read / write solution so that a lot of the missing things that people want can then be done.
-dro