Class restriction by gender
Solution 1:
Valkyrie is the only class that is restricted based on the sex of the character. Certain class/race combinations are easier to meet the requirements for if the character is male or female, but no others classes are available to only male characters or only to female characters.
There are certain items in the game that can only be used be female characters, and there's one item that can only be used by male characters but it can only be obtained by importing characters from Wizardry 6.