Because the pumping of chemicals to void them cannot be done quickly, a vent on the bottom of the vat that can be toggled like the normal one on the top to train liquids would be very useful when dealing with liquid byproducts

Likely won't make it in. The throttling of Mixture removal only occurs when Mixtures are yet to equilibriate. A better way to stop reactions suddenly might be to quench them with some other reagent.