I think the main problem is that the 'core' themes of the deformity feats have no meaning for warforged.

Sure, a warfored could stuff itself with junk (in theory, it might not be actually possible considering they're no more able to modify their body than a normal human. A warforged attempting to perform major mechanical change his arm is going to be in just as much trouble as a human is if he attempts self-surgury).

However, the whole point of the Obesity thing is that it involves the sin of gluttony: overconsumption and digusting waste for the sake of a carnal pleasure. Considering I don't believe warforged eat at all, and even if they do I'm not sure they have a sense of taste, they can't be 'gluttons'. They would presumably not gain weight or anything. At best they could mimic the effects of obesity through (theoretical) body modifications...which makes the thing seem silly rather than grotesque.

And doing things like filing down teeth and so on is bodily mutilation: causing pain and inflicting damage upon yourself in the name of a dark power. When a warforged's 'skin' is a shell of dead metal it doesn't have quite the same impact. Heck, I'm pretty sure there's already a feat or something similar that grants a warforged a bite attack, there's certainly nothing evil in it (making your teeth sharp to bite people isn't any more nasty that putting spikes all over your body to stab people)