It doesn't allow a heavier load on the airplane, but allows the same load to be distributed more lightly on runways. Many runway/taxiways will have load limitation based on the number of tires on the trucks.
One obvious modification would be the enlargement of the wheel well.
But that falls into my original questioning... did the wheel well even need enlargement? If not, then why not have it as an option on all A32x... which would give them [something of a] advantage over the 737 and its apparently limited wheel storage
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!