Random scheduled playlists

[pozhiloy-enotik]

I use the "Merge playlist to play as a single track."(merge_tracks) and radio = rotate(weights=[1,2000], [playlist_shit, radio]) playlist features to occasionally play songs of the same artist/genre in a row together.
Сome to the conclusion that a playing a full playlist of 54 songs would be not the best desicion, but picking 2-7 random songs from the thematical playlist and playing them at once might be better.

Actually Scheduled playlists with 10-20mins of playtime would work only if they had playtime & start time randomization.
The question is, is there any example how to accomplish this very rudimentary and demanded thing with the liquidsoap stuff?