NSEU,
Regarding Antiskid..... purely hypothetical but I will assume (there I go again) we're talking B744. I think the BSCU will ignore the signals from that particular bogey and pay attention to the other 12 wheel speed transducer signals that say, hey, we are moving at a great rate of knots here, and will continue with normal antiskid ops and the hydroplaning bogey will eventually start to spin up and join the antiskid party.
Regarding Autobrakes.... Agreed.
Autobrakes alone.... "The IRUs aren't mentioned in the A/B switch (1~MAX) arming logic on the 747-400."-- Look again. Agree with ground test scenario.
With regards to Att mode selected, I note that the IRS supplies ground speed, deceleration and pitch angle signals and arming logic requires valid Capts select IRS (ground speed and accel). With the loss of ground speed due ATT selected I wonder if your ground test would pass simply by the test looking at deceleration, pitch angle, air/ground mode, thrust and speed brake lever positions etc?
McHale.