Yes, this is an excellent idea … and it’s been talked about recently in the context of one shot parts as well.
I also think that using the AABACA music terminology in the song settings is a great way to add this feature without a huge investment in UI. It could just be a text box into which you could type “AABACA” … and that would be your song … and most people would instantly understand what it means
SS said it was something they would consider in the mid/long term. It would be a natural thing to do after one shot parts.