What if hit points were tied to BAB/THAC0 ?

first (pre-4E), do not roll for hit points; your class gives you MAXhp (class):

wizard: 4 hp/level 
fighter : 10 hp/level
 
then, every 10 hp gives you a +1BAB/THAC0 
so that a 10th level fighter will bear +10BAB, while a 10th level wizard obtains +4 BAB... 
How does that really differ from THAC0/BAB being tied to level and HP being separate but also tied to level?
Owner and Proprietor of the House of Trolls. God of ownership and possession.
Also, Next has no THAC0/BAB analog--Bounded Accuracy is awesome, by the way :D