I'm guessing that you're looking for something like the JTFE (Jump To File Extended) for Winamp by DrO - i.e. you want a feature where you can have your Now Playing set to shuffle while at the same time being able to pick and enqueue some songs that you would like to hear first - and once they are done playing MM just continues with the Now Playing in shuffle mode?
The lack of this feature has also been my major grief with MM for a long time.
Randomizing the Now Playing list and playing it in "non-shuffle" (regular?) mode whilst enqueing your selection with the 'Play Next' command just doesn't cut it

- especially since this solution will play the last enqueued song first :-/
The best solution I have come across so far is the
PlayNext script by raybeau528.
But this
only allows you to enqueue one file - it apparently does this by disabling shuffle mode when you enqueue the chosen song, and once that song start playing, shuffle mode is re-engaged.