Totally not stealing this class from Dragon quest 9 but you should make a gladiator class

kill quick if you're more interested in dark magick and assasination make yourself very visible so your friends ambush if you're begoming a acolyte or magician

hum well let us know what you like playing before asking what you want to be. what i mean by this is. What kind of person are you? do you enjoy the idea of protecting someone/some thing you love, do you enjoy the peace of helping others, or would you prefer to kill for the sake of anoble cause, do you enjoy the surenity of a battle, are you fine with just being able to help others when you can and are able to defend yourself? these are things you need to ask yourself before picking a class otherwise you'll go through all the classes till you find one you like. As for the question what class people like best it depends on the person you ask. this however is not the same question of "which class is the best". from one person to the next it's going to change based on game experiance and gaming style. For me it's the Knight i enjoy helping others and taking all the hits while defending my fellow comrades.

do a melody class (bit of everything)

And if we go with something completely new - how about something like a summoner ? I love to play with monsters that acompany me

How about adding the Taekwon classes ? Star Gladi and Taekwon Master rocked. Or the Ninja, I don't know if that would fit in RO2 but it still seems interesting to me. The Super Novice seems like a interesting suggestion too

I've played as all of the classes (Priest, Assassin, Sorcerer, Archer [Ranger], Swordsman [Warrior]) and my personal opinion is that I love playing as a Sorcerer. It's really just simply a personal matter about this. =p