I think it should be 4 Attributes for players And then rank them by grade(D-SSS). Saves from all the number confusion and overall makes it more of a broad meaning. So if you have higher grade in HP then you will have more health then the grade under.  I was thinking of the ones like:

-HP= Higher grade means Better health and defense.
-MP= Higher grade makes magic cool down's faster and more powerful.
-Strength= Higher grade means stronger damage with Melee weapons, Bows, and thrown weapons.
-Agility= Higher grade means quicker movement and faster weapon attacks/throws.

Take classes out all together, your stats build your class.Also I think their should be multiple humanoid races.

Honestly I rather have the story going in as we are all higher level players who just got stuck one day by what have you. But only very few players were on, like under 100. So everyone is there own little snowflake where all the stats, armor, and good shit is just for character fluff, the story lies around finding out what the hell is going on. Very much like the Overlord anime. But everyone likes their sweet character progression and SAO rip offs... so never mind this part.