plawolf
Lieutenant General
I think it has to be in the Computer interface although I do agree that you don't want it to be to easily confused for part of the fire control.
I would think a Key would be a better option something that the crew has to intentionally want to use and not a object that would be mistaken for something else. Because the VT4 and the ZTZ99A and A2 series fit in the "Advanced Third Generation Main battle Tank" It's systems are more reliant and integrated with computer systems compared to older vehicles. As Such If you can wipe the hard drive or lock the OS the Tank is dead. This differs compared to previous generations of MBT's.
I mean A First Gen MBT like say Type 59 is just a modification of a Tank dating back to the last days of World war 2. The Type 59 was production of a T54/55 which was a enlarged modification of the T44 which entered service in November 1944 ( didn't seen combat in WW2 by the Way. It was just being introduced. )
You jump to the second Gen like the T72 And more of the systems were electrical but the Optics and Fire control are still more analog. A captured model could be operated so long as as you had some electrical know how.
A key might be overdoing it, as I can easily see that being lost, especially during an emergency like the tank taking a crippling hit.
Last thing you need to do in that situation is root around looking for a key.
A good solid flip up over should more than cover it, especially if it is placed in a sensible, out of the way place.