I was putzing around with a Kensai build the other day, and it occurred to me that Aptitude works with any feat intended for a specific type of weapon--and that natural weapons are considered weapons.
Thus, feats that improve natural weapons should be fair game for Aptitude.
How far could that be taken? How would Rapidstrike and Improved Rapidstrike work? Would Improved Natural Attack be fair game?
For instance:
Let's assume I have a BAB of 16, the full TWF fighting chain, and a pair of Aptitude daggers. I also have Improved Rapidstrike (I'm a kobold with claws, y'see!)
Would I be able to take my full two-weapon attack sequence and then make up to four extra attacks with one of them because of Improved Rapidstrike (at the usual -5 per attack penalty?) Would those attacks be calculated using my highest BAB value?