Back when it was still the A3XX (in the late 90's) Airbus raised the subject of reverser's at a Configuration Working Group meeting and produced a paper showing the pro's and con's of zero, 2 or 4 reverser's including projected runway length requirements. Among the con's were weight, complexity, maintenance costs, etc and the fact the no reverser version was projected to require an excessive runway length for a wet/slippery runway whereas the 2 reverser version had a more reasonable required length. The airlines attending the meeting recommended the 2 reverser option.