If memory serves me correctly the installation of dual ice detectors goes hand in hand with the automatic nacelle and wing anti-ice optional fit. With this set up you put the anti-ice systems in Auto and if both ice detectors say ICE the anti-ice systems turn on automatically. Most 744's I saw had a single ice detector that simply gave an ICING message on EICAS and everything else was selected manually.
I think the difference in horizontal tail fuel usage between the 744 and Airbus is largely due to the fact that the 744 tail tank was grafted on to an existing structure and fuel system simply to squeeze in more gas whereas Airbus started with a clean sheet and the idea of using fuel movement for CG control from the beginning. I recall that early 744's had a Flight Manual limitation stating you had to land before gross weight reduced to a certain value if there was still fuel in the tail tank. Presumably a structural or CG issue. Not sure if this limitation still applies.