Lonewolf 50 -- The Goodrich pitot tubes are somewhat of an improvement, but they can still fail like the Thales tubes. Any shielding device would clearly need to be several inches behind the pitot tube opening when in the retracted position.
You are right about possible problems. If a shield system was not well engineered and thought out it could cause problems of its own. It would need to be as simple and foolproof as possible.
jcjeant -- I was not referring to the Apollo 13 pitot tubes . There was a problem during the mission with the ships air supply .The carbon dioxide scrubbers were inoperable because of loss of power in the main module .The astronauts could not wait for a perfect solution .They needed an immediate fix. It it involved duct tape and cardboard, but it worked