I'm having the same quandary over sashing. I think it needs something but it's a diagonal set quilt so any continuous design has to be spot on. The blocks are quilted right up to the sashing so there is a 2" or less area that is unquilted between all 16" blocks. The blocks are quilted with an Orange Peel. The setting triangles have a waterlily motif. The first border is a similar but simpler continuous waterlily and the final border is the fancier waterlily also continuous. For now, the quilt is loaded on the frame so I see it every time I walk into my office or past the window outside. Eventually a solution will come to me.
Back to your issue. How big is this quilt? Can you post a pic? What kind of other quilting designs are going on in the quilt and how close do they come to the border?