It's too bad there aren't any mods that give the user a brain (not that it's needed anymore
), but if you feel your guild is really in need of requirements for the current content, you probably want to keep it simple. To a lot of people (especially those who know what they're doing), requirements can sometimes push away the more skilled players. Also, mods are only as good as the person using it (and how un/familiar they are with the mod can sometimes not give the results you intended).
That being said...
1) Ventrilo (not a mod, but it has better results than 'in-game' chat).
2) Omen (or a compatable substitute threat meter)
3) DBM or BigWigs
4) PallyPower (Paladins only)
5) An alarm clock implanted in their head, rigged for electric shock if they're late for a scheduled raid.
Now if your heart is really set on being mod Nazis, you might consider...
5) oRA or CT_Raid
6) Decursive or SmartDebuff (class specific for those who can cure/dispell/remove debuffs)
7) SmartBuff for classes that have a 30 min or longer buff to apply on other players.
There are others, but really, when you start dictating how others play a game, you might want to take a very deep breath of fresh country air
.
Good luck and be careful.