K, since pretty much everybody ignores your question, you have 2 scenario's IMO
You keep wobbufett because you obviously like it, but tell your opponent before the battle. Many of the challengers won't fele like battling Wobbufett though ;/
Replacing it is hard, though seeing as you are a defensive Pokemon trainer, a Steel type might be a good choice, since you lack a good physical wall. I personally love Steelix, who has nice attack and incredible defenses. It can lay down a Stealth Rock, Roar Pokemon away, Earthquake with stab, Explosion is always nice, and Gyro ball alows it to seriously dent alot of pokes too. however, it's low speed speed and special defense are a real let down. But, with blissey taking up the special attacks, this is probally no problem.