Describe your question better. What do you mean with "calculating exp, hp, sp, mp"?
If you mean Gear base stats, and that is my main concern, I would'nt calculate those because Shaiya does not need custom gear.
But if you really want to mess with the games overal purpose and balance, I'd only increase the base stats for the new set by taking the base stats of the current best set and multiplying them by up to 10-15%.