If putting the blight in the game is so easy because it just requires a cloud over the map, that still more or less fits with the idea of shrinking continents by just making regions unavailable. To use my examples again, blight clouds = storm clouds over flooded regions, smoke clouds over lava regions, or just use blight and call it unknown black magic or the result of something nefarious that spread as a result of the invasions on BT.
If modifying continents is too much of a hassle for the coders, though, just pick one and sink it if changing the size of the game is the best possible solution to fixing player density problems.
