It is a good idea on a sub-playlist widget, each time the new sub-playlist is generated to have the option to get the random item(s) from the pre-defined playlist. This guarantees that on the next loop of the playlist you will have different content for the audience.
For example for content in our hospital infochannel we created short movies with different subjects: Travel, Health tips, Fashion, Fitness, Food facts, etc. I have different playlist for each subject and in the layout sub-playlist widget, set to get one item from each subject playlist. Between the loops we have new layout with Adblock. Unfortunately on every loop it creates the sub-playlist with the first item from each subject playlist. It will be good to have an option to create the playlist with a random item from each predefined playlist. That will ensure the audience is seeing different content in the loop.