Your steering lock is classed as one security device and your car keys another, plenty of cars passed iva like this
I have a battery cut off behind the dash but its panelled in on the underside so wasnt visible at iva
I can snake my arm round and switch it off when needs be as i know where it is
If they know its there at IVA it possibly may cause a problem using it as a security device because for it to disable the car it will be turned off but this means your hazards wont work which they obviously need to!
You could wire them seperate or put a small rated fuse across the battery switch which would let the hazards work but would blow if you tried to start the car without the main isolation key being turned on
Just read Enochs post so ignore everything i said above as you cant use it as a security device anyway!