On the subject of the A380, an alternative to reducing the number of reversers being studied by Airbus was dropping them all together, that decision came about as part of a massive weight loss and cost cutting program circa 1998 with the aircraft on offer at that time being not being anywhere near close to the ~20% cost reductions that Airbus wanted (and needed to sell any) over the 747-400.
To quote from 'Airbus A380' by Norris/Wagner,
Another cost and weight saving change discussed at great length with the airlines involved reducing or eliminating the use of engine thrust reversers. As the name suggests, these devices redirect the engine power - or some of it - forward to help slow the aircraft after touchdown. Whereas some early low bypass engines redirected all thrust by blocking the entire flow out of the exhaust, the later generation and much larger high bypass ratio engines deflected only the bypass stream. This limited but valuable reverse thrust was generally seen as a supplement to the stopping forces and helped reduce break wear on landing.
In itself, cutting wear and tear on brakes was a major cost saver, and the decision to eliminate some of even all the reversers was not to be taken lightly.
Airbus canvassed airlines on the proposals about November 1998, emphasizing potential weight saving and performance improvement from the the move. In the end, a compromise was reached and the reversers were dropped on the outside engine pair only, particularly since most airlines agreed that the increased braking thrust, from the improved efficiency engines to be used on the A3XX would help achieve a predicted stopping distance similar to, or better than the A340.