The basic concept would be, what if Professor X, or in this case a mutant mentor figure very much like him, were every bit the nefarious exploiter of children in his care that the most rabid anti-mutant bigot thinks he is? The set up would be the same, mutant teenagers discovering their powers and being recruited into an organization teaching them to use their gifts, only this time, its not for the benefit of mankind, or its destruction. These are the mutants who shy away from the big apocalyptic battles of good and evil and just want to make as much money as possible. Some of them are used as the public face of a PR campaign to re-brand mutants into a marketable product, while those not photogenic enough or with more specialized powers act behind the scenes, often in criminal enterprises, or using specific powers for very specific for hire purposes. The idea of a mutant team in and out of the public eye would be approached with the callous opportunism of a multi-media corporation, with "heroes" displaying an at best apathetic attitude to actually doing good, at least at first.
Their leader would be a man calling himself Mr. Destiny, a mutant with the ability to find other mutants and see their potential. He's not a full psychic, but rather has the ability to absorb and analyze ambient psychic data accumulated around a person to predict the probability that they might perform any given action. Basically he can perform a generalized version of Saber Metrics in his head, but with people, and based on any criteria of future performance. He can look at a person, ask himself what the chances are that they will be president some day, and receive a psychic read out of the various probabilities according to different variables he suggests. A side effect of this ability is the power to detect mutant powers and gain a general idea of how they work, allowing him to act as a teacher as well as an agent steering the fates of his charges. He wouldn't be so much an evil character, just amoral, a sort of Fagan-esque lovable criminal.
I didn't have a full roster of characters, but I tried to think of teens with powers that either lent themselves to unsavory activities, or that would logically ostracize someone enough to lead them into the waiting arms of a group like eXcel. Their leader would be Pretty Boy, a mutant with the ability to psychically manipulate the pleasure centers of other people, making them like him automatically or fall instantly in love with him, which he would use to engender himself to the public, while secretly indulging in all manner of sexual deviance just because he can. The Rogue-like unfortunate power carrying mutant was Cinderella, who turns everything she touches into glass, which she can then control telekinetically, after transforming her entire house and family when her powers manifested. Finally, for the teenage metaphor hero, there was Outburst, who transforms into a series of Hulk-like super powered alter egos corresponding to various emotional states whenever his get out of control.
The idea behind the title would be that it would subtly change as the story arc required. The original title eXcel would refer to the organization and its stated mission of letting mutants reach their full potential, but eventually the true motives would be revealed to those not in the know, and the title would change to X-Sell. After breaking away from Mr. Destiny and forming two independent teams, one a noble group of superheroes and the other an unscrupulous group of criminals, the name would change to X-Cell, to represent their status as mutant terrorist cells as seen by the U.S. Government, and later when it would become a jail house drama as the groups are both detained in a super prison. Eventually they would escape and attain a level of underground, counter culture celebrity, recruiting a large fleet of new members and finally changing to X-L. The idea would be that in the end, the team would come full circle on the other end of the Civil Rights question, becoming a sort of militant equivalent of the Black Power movement without the mutant community.
Obviously I never pursued this past the initial pitch stage, and eventually I would cannibalize most of it into my larger original comic book universe under different names. As always, I have no other place to vomit out this stuff, so hope you enjoyed it, and I'll see you tomorrow.