I did it. I got SRTT to launch (apparently there's a common problem on Steam where it doesn't download the first time) and I successfully altered Kinzie so she is dressed like Anna (the short shorted lady biker saint), and replaced all the generic saints with Swat/Masako. Some issues though, it changes Kinzie's glasses into sunglasses, and it tries to put a bandana on her head (Kinzie's hair clips though it).
I'm looking through the extracted files for both SRTT and SRIV, and I noticed that Shaundi and Kinzie have two entries, one npc and one saints_female. I open them up with paint net, and they're identical. With Kinzie in SRIV I went ahead and changed both of them, but game wise, what's the difference?