But seriously - Happ is on track for about a 4 b/fWAR season, which is really nice, but he's around for two more years at most and he's going to get more expensive. He also doesn't have any track record to repeat this performance, and he sucks on defense. This trade would leave the Sox with a RF hole still, and it would trade away their heir apparent to that position.
Someone like Burger would be a better fit for a Happ trade, I think. Cubs can play him every day at 3B/1B/DH, and I'd bet he'd be a solid contributor for them. Include a lower level arm (Kelly/Thompson/Dahlquist, for example) and I think you have a start.