RAM isn't ROM. You can't expand RAM. And you can only have 128kilo bytes in one save file. Though, it seems there is some unused RAM in the area after ~ 0203E000 which I suppose could be put to the saveblocks.
Actually if we assume that the area 0203E000 0203FFFF is all free, that leaves us with 8191 bytes. Since one pokemon takes 80 bytes, we could have around 100 additional pokemon along with boxes' names and the wallpapers. We could get rid of the checksum and 2 not used bytes in the growth substructure, so the pokemon would be 96 bytes long, which could enlarge the boxes' capability.
There's also 240 bytes of DMA in the saveblocks area, so that could be used as well.
If you didn't understand anything of my rambling, don't worry. The takeoff is that the expanding the box space is a hard and complex thing to do that requires fiddling with the save files and RAM areas. And I don't think making a patch for it would be a good idea since it'd use lots of space that could potentially be used by a hacker.