What Works and Why: Opus Magnum
One thing I would like for the Zachtronics games is if the optimization mattered somehow other than just personal satisfaction.  Such as you get achievements, special equipment, or get to unlock special stages for meeting certain optimization goals.  Or since you are basically designing factories (or PCBs in the case of Shenzhen and TIS), maybe your creations earn profit based on their cost and efficiency?  And maybe you have to earn enough profit to win the game, in which case would have to revisit less efficient designs to improve them.