I'd love to see the productivity recipes requiring the item you're researching as a cost.
Wanna increase the productivity of the rocket control unit? Yeah you're gonna need some ammount of rocket control in that research.
I just have no idea how that would be implemented in the lab. Maybe a new building used just to pay the costs of productivity researches?
We were actually considering exactly this.
But the reason we declined this idea was, that having one central resource (the whole research) improving one specific thing is more strategical compared to just "sacrifising" some part of the production to make it better over time.