would you need to wear them the whole time? IIRC you only need focus components at time of casting?
Is this a valid item to purchase? the Potions section is incredibly vague on what can/can't be a potion or an oil and appears to say any non personal 3rd level spell with a casting time under 1 minute that targets people or objects can be made into either a potion OR an oil (though occasionally only useful in one form)
As far as Seamless Shapeshifter and Realistic Likeness goes, it doesn't matter what the source is, they're both Circumstance bonus' affecting Disguise so they won't stack, nor will the disguise kit for that matter. The only typed bonus that stacks is dodge or anything that says so explicitly which this does not
From how i'm reading the retraining rules, the feat has to be chosen from the pool of feats that the feature granting the feat gives access to regardless of the level you currently are. So I guess the real question is more the question of are the additional feat options added to the pool even though you would never normally gain access to them.