Not yet! But it's in the plan...someday...
I would foundation piece the stretchy velvet, but if it is the heavier drapery/upholstery velvet, I see no need.
You need to be aware of the fact that velvet has a directional sheen. Because of this, two pieces from the same fabric will look different if they are not both placed facing the same direction (upside down/right side up). This is not always an issue in a quilt, but can be very much a problem in something like a dress or a cape.
Can't wait to see your finished project! Sounds like it will be gorgeous.