Would it be possible to make a simple system where if Lona gets repeatedly raped for certain amount of days she starts to react more obedient to her captors? I read that her siding with the enemies is not planed anymore but what about just submission? For example she gets captured by gobbos. At first she will not want that but if she stays there for around 10 days every time they rape her she enjoys it embracing her situation. With an expression of joy, maybe even give her some addiction debuff that makes her want to screw with gobbos, fish people etc. and only gets removed very slowly with time or from the help of an NPC. 

Or at least make Nympho Lona have happy facial expressions and lines when she engages in sexual intercourse be it willing or not. 

Thanks for reading.

Go to the "Traits" Options , You will see a skill name "Masochist" , Use trait point on it and Lona personal will love the violence. I think this is the closest one to your proposal.

MMmmm.... well for mental breakdowns...
So far we only got 1, and its that if you betray Cecily you will get occasional nightmares that will give lona a big mood debuff(PTSD).
but what you want is currently a Trait thing only, by changing personality.
Lona does already grow submissive when captured and got a gameover in the Fishtopia cave, where she is totally okay and happy giving birth there many times because Deepones gives her life necessities, Sleep in the Cave in a Captured state and then click "i give up", i think you need negative stamina for it.

TLDR: We kinda have it, but not exactly, Wish that it gets added later! :thumbsup: