Disguise is a skill reflecting your skill at changing your appearance. It uses the Charisma stat as a modifier
What can you do with Disguise?
It is your ability at changing your appearance. When you do you make the check once, and everyone then uses that as their perception target number.
It is assumed most people are taking 10 on these checks, which is another example of the elimination of randomness among the use of the skills.
Which of these have ground for use?
I think this skill is one that clearly falls under the 'no skill is necessary' category. It comes up rarely enough that we probably don't need a system for dealing with it.
The ability to give a target number that once passed means the skill is seen through.
What do we lose?
A good deal of play. If we work from the assumption that the skill provides, that most characters with a minimal skill or a first level spell will be able to disguise themselves beyond cursory detection, then we create a situation where the only time an actual roll is called for is when the character does something suspicious.
Why are we bothering to roll the dice at all? What benefit to play does it provide?
Some people might complain that certain players might not be as good at these things as others. That is a core feature of games - not a bug. They require skill, not just luck. So there is nothing wrong with smarter more social people being better at play, and players who are not social or creative or intelligent being worse and losing or doing badly on their own merits.
This, I think, people need to realize applies to life.
Conclusions & Suggestions:
My preference is to eliminate the skill and simply assume the player can disguise themselves effectively. Then I would allow the players own skill at research and fast talking to represent their success.