I think removing the songs/stack is a great idea. PNMs will definitely notice this if it's something every other chapter is doing. For campuses that have less frilly rush, maybe limit the amount of sisters who are allowed to table, or limit the advertising for that group.
The problem I see with the suggestion of not allowing the sisters who dirty rushed to participate in a round the next year is that chapters who dirty rush would just have their seniors or girls who were studying abroad do all the dirty rushing since they would be "losing" them the next year anyway...at least that's what I'd do if I was in such a chapter.
