maybe designing for individual clients?
persons, a smaller group of people, etc.
bridal shops and tailors work this same way
and you may get some ideas from reading about how Illustrators/graphic designers work
because they also change from client to client
Where I work we do custom designs
and customers will say for example, they will want to use a font we have in our logo to be used in their shirts or to move textile print designs around on clothing, to change colours or add new images to the design, etc.
I don't do all of the work, but from what I see it's all up to our designers
but I know this isn't the case for illustrators --Some of them will be in constant contact with the client, say after a certain amount of time they will have another conversation
You might get some ideas in this other thread:
http://www.thefashionspot.com/forums/f90/freelance-fashion-designers-there-such-thing-73873.html