- They must remain true to the nature of the base class: a Fighter variant must still solve problems physically, a Charmer variant must still solve problems socially. Use the attributes as guidelines.
- The replacement power must be no more powerful than other class powers of the same type.
- The variant class should not be designed as if it were a profession (use backgrounds for that.
Variant classes are named after the base class, with the variation in parentheses: thus, Fighter (mighty thews) might be a reasonable name for the above example.
The most obvious variants are the supernatural ones, as alluded to in the Gifted post: a new class can be based around a replacement spell list, like Magic-User (illusionist) or Cleric (druidic.) A player can work with a GM to make a custom spell list with modified rules for spell use. Instead of beefing up spells in return for potentially meaningless class limitations, attach limitations to the new type of magic itself; for example, if you don't want Magic-Users or others using the MU spell list to use armor, this should be a feature of MU spells (armor causes spell failure, or slows down casting, or some other limitation.) A Magic-User can wear armor and not use magic, while a custom Elven Magic spell list might allow wearing magic armor, but have reduce spell power and variety.
Variant classes are not otherwise limited, and use the experience and HD progression of the base class; hybrid variants, like Hybrid Fighter (mighty thews)/Cleric (druidic), use the appropriate hybrid experience/HD progression.
Modification Type Three is tomorrow.