In the end, I kept the easing in the side seam. I also left the neckline shape as drafted. The velvet tends to fold back quite softly so I think this will be fine. Instead of a 1.5cm hem, I overlocked the raw edges and decided to leave them as is. While this jacket doesn't wow me, I think it's wearable as a casual throw on cardy. Better still, it means I can wear the teal Tee I had in the wardrobe. I had made this T-shirt from a lightweight poly knit (Manhattan knit from Spotlight) and unfortunately it was just a bit clingier than I liked. This jacket hides that. :) I played around with the ribbon placement and then decided to leave it off. A waist placement was not a good look. DH did think it looked nice with ribbon under the bustline but there's a limit to how much emphasis I want to put on that area! Instead I've settled for a pin to hold it closed.
(What a terrible photo - I look like I'm falling over... or drunk!)