Cool, I'm counting ten interested so I'll start working on a more detailed write-up. While I'm getting the behind-the-scenes stuff ready (I should have most of it finished by Saturday night), I'll put a character sheet up tonight so that everyone can start working on a character.
Empyrean: I remember Coltrane actually. I played Joshua Donnelly, and a few others that never amounted to much. Josh was my big dog! I might need to pick your brain about what you remember about Nexxus, it's been years since that was running.
For the classes, I did a casual search when I wrote the original post to try and find something that clarified the classes a little more. I think Marvel may have changed it again, because I found a lot of references to "Alpha", "Beta", "Delta", and "Gamma" mutants, but nothing specific to Class 1-5. I'm going to keep looking.
I found this on an old board.. it's not the greatest, but it's a rough guide to the types of mutants.
The Alpha Mutants are the most powerful and most feared mutants. Alpha mutants have extremely powerful mutant traits without any significant flaws. Less than 10% of mutants are Alpha mutants so they are very rare. Some of the Alpha mutants include Gambit, Professor X, Colossus, and Emma Frost.
Classify Mutants as Alpha level if they have a normal human appearance and their mutation is powerful, useful and controllable (i.e. turn it on and off, direct it at will.)
As far as how potent their powers are Beta Mutants are on the same level as Alpha mutants. The difference between Beta Mutants and Alpha Mutants is that the Beta Mutants have flaws, albeit very small flaws. The Beta mutants are also believed to be about 10% of the mutant population. Some examples of Beta mutants are Wolverine, Mystique and Sabretooth.
Classify mutants as Beta Level if they have a normal human appearance and their mutation is powerful, useful, but less controllable, like Cyclops who can't turn his power off, but can still lead a normal life with only minor preparation. Wolverine, who has healing powers, can't ever decide NOT to rapidly heal from an injury, but this does not impair him in any reasonable way.
Gamma mutants have very powerful mutants but they have flaws. Unlike the Beta mutants a Gamma mutant's flaw is a major flaw that makes their life very hard. The best example is probably Rogue. Rogue can absorb anybody's power, which makes her very powerful, but she can't touch people without triggering her power, which makes any kind of romantic life difficult. Also, while Alpha and Beta mutants can pass as regular looking humans, many Gamma mutants cannot because they have physical deformities like Blob or Marrow.
Classify mutants as Gamma Level if their mutation is powerful, uncontrollable, sometimes useful but usually detrimental to living a normal life, such as a monstrously inhuman appearance that can't be switched off at will.
Delta Mutants are like Alpha mutants in that they don't have any significant flaws. The only problem is that Delta mutants don't have powers that match an Alpha mutant, or even a Beta or Gamma mutant. At least 50% of mutants are Delta mutants making them the most common type of mutant. Some examples of Delta mutants are Forge, Domino and Callisto.
Classify mutants as Delta-Level if they have a normal human appearance, but their mutagenic powers are weaker or only narrowly applicable, though still controllable.
Epsilon-Delta Mutants are mutants that don't always manifest their power. An Epsilon-Delta's power will only manifest in certain circumstances and they don't use their powers very often. Their powers may manifest due to trauma, influence from somebody or somebody else or physical contact with someone.
Classify mutants as Episilon-Delta Level if they have a normal human appearance and their mutation is relatively weak, uncontrollable, and narrowly applicable.
Epsilon Mutants are unfortunate mutants. Epsilon mutants pretty much have no chance of having a regular life in society due to their major flaws. If that isn't bad enough Epsilon mutants also only have minor superhuman powers. About 20% of mutants are Epsilon Mutants. A good example of an Epsilon mutant is Beak.
Classify mutants as Episilon Level if they have an inhuman appearance or their mutation makes it impossible for them to function normally. Any accompanying "superpowers" would be next to useless. Epsilon mutants are differentiated from Gamma mutants in that a Gamma mutant's inhuman appearance would provide a compensating benefit like superior strength.
Omega mutants are the most powerful class of mutants. Omega mutants can control matter and energy, have unlimited potential and are possibly even immortal. All Omega mutants are also Alpha mutants but not all Alpha mutants are Omega mutants. For example Jean Grey is an Alpha mutant because of her power and lack of flaws and is also an Omega mutant because of how powerful she is. Gambit on the other hand falls under Alpha mutant for the same reasons but isn't powerful enough to be an Omega mutant.
Only classify mutants as Omega Level if they have been explicitly referenced as Omega Level within continuity or if they regularly match the feats of a known Omega Level mutant.