Then install another turnstile in the current emergency exit. You and the LRC apparently share the goal of keeping unauthorized computer users out of the lab. The question you raise is how best to do this. I am not sure why you would prefer a turnstile to showing your I.D. to a fellow student, but I do know from past experience that many people profoundly dislike turnstiles in libraries.
Turnstiles can be especially awkward for law students with large bookbags or backpacks.
They are also a problem for handicapped patrons, especially if they are in wheelchairs. So, while you might prefer mechanical access control for the lab, we know that many others would not. If you forget your card or lose it, a turnstile will be much less forgiving than the human beings working in our lab. Fire codes prohibit installing a turnstile in an emergency exit, but we know it sometimes gets too hot and stuffy in the lab. We will be replacing the solid wood emergency exit door with a louvered door that should increase air circulation.