Benji Dunn: Join the IMF and see the world. On a screen. From a closet.
Ethan Hunt: The Syndicate is real. A rogue nation, trained to do what we do.
Benji Dunn: An anti-IMF.
Benji Dunn: Let me guess. Presumed dead?
Ethan Hunt: Well tonight, I just made it official.
Answer: This plan is not discussed because they may not have had the hacking skills to take control of the robotic arm. Regardless of whether or not they did, it would not have been the best idea as they are supposed to be infiltrating the facility in complete secrecy. The plan of Ethan holding his breath underwater and manually planting the cards into the system is a lengthier plan, but is less likely to result in them being caught.
Casual Person