re: Chemical reactors might be more useful than just stripping the atmosphere
Chemical reactors to process the CO2 into some other form might be more useful than simply stripping the atmosphere. If the goal is to create a planet with life, just like earth, then:
1. We remove enough CO2 to bring the temperature down to between 10-45 deg C. on average to allow photosynthesis. The carbon should be sequestered temporarily until plants are thriving. Oxygen can be reacted with anything, perhaps with nitrogen to produce fertilizer.
2. As plant life converts more CO2 to oxygen, the greenhouse effect on Venus might become less, and the temperature will drop. To prevent an ice age, the previously sequestered carbon might be re-released into the atmosphere bit-by-bit to keep the temperature acceptable.