EMC has updated to 1.4 on 31 October and something will eventually be done - hunting down the wither. This was all done on EMC. Extreme hills biome seems suitable... Not as amazing as I imagined, but yay!
A team of 4 was looking for wither skeletons in a large fortress in the nether of smp6 for almost an hour - we didn't see any. Only a ton of zombie pigmen, some of them with pumpkins on their heads...