So as for that "heaven forbid" part.... here's the work out of the possible stacking methods.
List is based on a lvl 8 bloodrager.
Size=lvl4 abyssal bonus, INA=Improved Natural Attack, RS=Rageshaper(assumed to be +1 die)
(this last one assumes d8 progression here happens like stated in INA for d10 type weapons)
So as we can see, in half the methods (1, 2, 4) INA does absolutely nothing. In methods 3 it actually brings your damage down (by only .5 on average, but taking a feat for less damage! Maybe you feel too powerful... here's you're out :p). Last but not least it's obvious that RS applying first gives us the best benefit, whether we have INA or not (without gives us 4d6 as large vs 3d6 if large applies first) INA also pushes our damage into the ridiculous category!
So cheers to those of you who have DM's that allow monster feats on PC's that qualify (make sure you stack your bonuses right!)