What are thoughts on making Windup a Sorcery-speed activated ability only? Wizards had a reason for making Outlast from Khans be Sorcery speed; instant speed activation makes it too easy to play "Draw-Go" control style and leave creatures untapped as blockers, then activate when opponent goes to his end step.

While our new version of Windup has some similarities to Outlast, I'd say it was closer akin to Cohort from Oath. You'll notice that, while both involve tapping creatures, one is sorcery-speed and the other instant-speed. Obviously that implies that even Wotc is willing to push things a little further when they feel it's useful to the set, as it is here.

Having windup be sorcery speed or not has been an ongoing question since the creation of the mechanism. At first we were worried it might cause too much board complexity, and I am still not sure if it does or not since we have not had enough play testing done to confirm one way or the other. The sorcery speed got removed when, about mid development, Oath of the gatewatch came out, proving that Cohort does not need to be sorcery speed.

I would be one of the first one, however, to return back to sorcery speed. Cohort is not equivalent with Windup. Cohort avoids for the most part board complexity, with cards creating either card advantage, dealing direct player damage, or in the case of Spawnbinder Mage, simplifying board position. The only cohort card that significantly increases board complexity is Munda's Vanguard. As a comparison, every single Windup card we have increases board complexity if left at instant speed, which is not something I am comfortable with until play tested intensively. This places Windup closer to Outlast, which needs to be sorcery speed to be at common because instant speed buff increases board complexity, than Cohort.

I hope this answered your question?