I do like the idea of the residents only stepping in if there is a shortage of floor singers. I met an organiser of one club who did not go to another local venue despite the good acts because they always had the same support act.
We used to have really good sessions with the morris side with usualy one individual spot for each person who wanted one then tune sets and songs for all to join in singing and/or playing along to. As an organiser I would only do a solo if there was no one else, which was fairly infrequent. The policy seemed to work as we usually had good post dance attendance and many of the publicans claimed that it was the music they really enjoyed.
I also like to see the main act in a folk club audiencing the floor spots. I think it shows a discourtesy if they dont.
FloraG