my lapse aside, in 'animorphs world', is that fact stated somewhere? that's something else that i've missed. i'm kinda extrapolating the theory that DNA is human existence, ergo how could acquiring human (or animal) DNA and then morphing not then also create sentient life that is less than an actual person (animal)?
They morphed Leerans and didn't have any issues with a "conscious" showing up. I think that's the longest they ever stayed in a sapient morph, but Tobias morphed Andalite, Marco morphed a guy at one point to escape some building. Ax had a human morph... actually, I stand corrected, Ax morphed human all the time.
I don't think Cassie started out so extremely... weird about fighting. I mean, she was ok with destroying the Kandrona early on, but wasn't ok with destroying the yeerkpool. They would do the exact same thing, so it didn't really make any sense. (makes less sense V3 was ok with letting the pool get destroyed if all his minions would starve to death, but whatever, that book was badly written).
I think she started out being ok with fighting because she knew that someone had to. I don't think she would volunteer, but she wouldn't back out on her own. The only reason she freaked in book 19 was because she had a severe stress reaction to Jake almost dying in 16. KA set that up really well. Anyway, I think before ghost writers took over she was okish. She nose dived pretty fast after that. I think the wolf morph was just because. She had something that kinda worked and fighting wasn't important to her so she never bothered getting something else afterwards. I mean, she didn't even have a real battle morph until after they picked up wolves for an unrelated reason.