1) A place for a person signing up to type in a comment (other then the late field) so they can put in notes such as their role in the raid (ex. a priest can type in DPS or healer)
If you define Roles and use Role based signups you can fix this on your own today.
Examples are to create Roles for the following main types for raids.
Healer
DPS (this can also be split into 2 roles. 1 for melee and 1 for ranged)
Tank
Under each Role definition you check off the class allowed to sign up for that position.
On your calendar events you change the option to signup type from By Class to By Role. Signup by role was an implementation request a while back that should help you with the issue of a priest that is Shadow versus Holy and a Paladin that is Retribution, Protection, or Holy as they will be able to pick the role they will fill in each raid. The advantage of this is that you can also assign numbers of each role you expect to have (ie 2 tanks, 3 healers, and 5 dps) for each raid.