Buzzsaw will appear in the blueprints instead of the Acid Bath. If you’ve got an Acid Bath installed at your base, it’ll turn into a Buzzsaw.

❓ Do I need to seek out the blueprint for the Buzzsaw in Bunker Alfa, like I did with the Acid Bath? 
There won't be a blueprint for the Buzzsaw in Bunker Alfa. It'll be unlocked once you complete chapter "Iron Warrior", after completing quest 10, "Chopper", in the Survivor's Path.
❓ Where do I bring infected and sunken boxes if there’s no Acid Bath anymore?
The buzzsaw can take care of those as well.
❓ Can I cut new crates with resources open with the buzzsaw at the Farm?
No, the buzzsaw at the Farm won’t cut open new crates with resources.