I understand that the proposal was to replace the t&B/TC with a second AI, in that position, but doing so would not conform to the design requirement stated. Though you still would have the original AI in its proper position, the design requirement does not provide for also providing that information in a non-conforming location on the instrument panel (and prodiving the expected T&B/TC information elsewhere).
In instrument flight, there is an expectation of an effective instrument scan, with the pilot finding information in the panel location expected. A second AI in a non conforming location has to potential to disrupt this. Not having the T&B/TC there certainly does, were "needle, ball and airspeed" flying become necessary.
If a second AI is proposed, it should either be in the corresponding copilot's panel location, or top centered, as is common for glass cockpit aircraft.
Instrument location in the panel is one of the times when standardization for flight safety is a very good thing.