Julian,
Au contraire - you don't seem to understand the ILS, the ONLY time you know where you are on the GS/loc is when the needles are centred. You are then precisely on the localiser and glideslope, which is the ideal place to be when you arrive at your DH/DA in minimal weather conditions if you want to be ale to effect a safe landing. If you are off to one side or high/low you only have an approximate idea of where you are, based on your distance from the transmitter (and very little idea at all if the DME is u/s as it's difficult to factor in the 1:60 rule then). It is also less likely to lead to overcontrolling. I can only say again that if you fly at half scale deflection on either localiser or glideslope, and make no effort to correct back within a reasonable time (say 2-3 seconds) you will fail your IRT. The approach is not 'required to be flown to 1/2 scale deflection' - it is required to be flown with the needles centralised, with a MAXIMUM occasional deflection to no more than half scale.