Interesting that you're posting in a game development forum with an idea for a fictional MMORPG that takes place inside a LN. Still, I understand why one would do this, as I appreciated the numbers present in SAO and in 1/2 prince.
It's very useful to be able to make up new things in a work of fiction, as the characters begin to face more diverse opponents, some of which may be more rare than others.
Also, from what I'm seeing, stat increase is relatively linear. This would also mean that the danger that a lvl 20 poses to a lvl 10 character is smaller than the danger that a lvl 80 poses to a lvl 70. Also, I may be mistaken, but the hp of a lvl 100 character appears to only be about 6 times the hp of a lvl 10 character, which one may want to reconsider.