Alright, first off, like I said, this Richard Castle is becoming world weary to his fame and the things he has to do for publicity. Meeting Kate Beckett changes things in him and he starts writing again. He gets a few chapters of Heat Wave written and hands them to her to get her opinion of his new character and basically ask permission to use her as a template for Nikki Heat. This leads to them sitting down for coffee one day and he opens up to her, about his life before he started writing, the story behind his marriages and divorces, and finally why he decided to kill of Derek Storm. She cannot believe he would tell her, a virtual stranger, all of this, but he assures her that he feels that he can trust her and that he's never confided in anyone about all of this. She's actually touched and after careful consideration, decides to reciprocate and tell him her story. It's emotional, but he doesn't pity her or anything.
One thing he does do is ask her for copies of the case file and anything Johanna was working on at the time of her death. At first Kate balks, but he explains that he has friends in just about every government agency and that many of them owe him favors (and many of them would do just about anything for him just because they are his friends). She had said that she couldn't go down that rabbit hole again, and he agrees, which is why he wants to hand it off to people that can make discreet inquiries without shaking any beehives. She agrees, much to his surprise. She also preempts him by saying that she will allow him to shadow her to get the research he needs for the book, since while he seems to have some of the details right, he got a number of them wrong and it would be a shame for the book to have things wrong.
Before the show's second episode, they work together on another case where the victim has no visible cause of death. It will lead them to what looks like an abandoned lab, but while searching a glass wall will separate them while walking through a hallway, and a strange gas will knock them out. When they come to, the entire facility will have been cleaned out and there will be no indication that anything is there. I'm not sure if I want the dead body to just disappear or to have some kind of government agent come along and take possession of the body. Either way, the case goes unsolved and Kate and Rick go to their separate homes. As Rick is going home, he thinks people are just more talkative than usual, but once he gets to his office at home, it's like someone opens the floodgates and he's receiving the thoughts of everyone for a pretty good distance. Kate gets home and that night while looking in the mirror she wonders about her hair and suddenly it starts changing to what she was thinking about. It freaks them both out, and she winds up going to see him to see if anything strange is happening to him as well.
Somehow Castle manages to figure out how to limit his mind reading to just Kate, and that allows him to speak back to her as well, and Kate works out that she can change anything about herself (by accidentally becoming his clone for a few moments). When asked how he figured out to do what he did, he said it was about focusing just on her and thinking of it like the difference between a receiver radio and a telephone; he can either pick up everything around him without being able to respond, or he can make it so he can only hear one and can answer back. I don't know where else to go with this so far, but the point is that Kate will be able to make it so she's impervious to bullets by making her skin under her clothes more or less bulletproof, and their relationship will take much less time to mature, meaning they will be together far earlier.
Now this one I had said I wasn't 100% sure I wanted to bring up, because it involves a more adult storyline than all the others, but I've got ideas so let's do this...
First is Richard Castle, who will actually be Erika Rodgers, but when she tried to get In a Hail of Bullets published, no one would pick it up (outright rejected was more like), but working out a little, taping up her breasts, and practicing her voice to be deeper and more gravelly, suddenly everyone wants to publish Richard Castle's book. Oh, further I'm changing it so that she and Kate Beckett are the same age and that Erika had Alexis in college from a man she only met once while shadowing the CIA and not from any college sweethearts or marriages she ever had. When Alexis is about 7, she gets in on the game of playing that her mother is actually her father, thinking it's a fun game to fool people.
Now Kate Beckett is also a very different person. She was born different, however, and has had to adjust her life to reflect that. She was born a fully functional hermaphrodite which made things awkward growing up. Because of this, she has never actually had a relationship with anyone, meaning no fake-but-not-fake marriage in Las Vegas to a college boyfriend. One thing, however, that is just a fact of biology, is that she able to sense the pheromones of males and females separately, meaning that she isn't fooled by "Richard Castle" and confronts her in her home after the case. Erika and Alexis are really impressed that she figured it out, and Erika isn't ashamed to admit that she's a little aroused by that, too. Kate Beckett is taken aback by Erika continuing to flirt with her, regardless, but Erika won't back down. Heck, she's intrigued when Kate reveals her secret (thinking that would be the only thing to turn her away, falsely believing Erika to be a lesbian).
The entire point to all of this is that I want them to not only easily fall into a relationship, but I want Erika Rodgers pregnant early on, so that there is plenty of chance for these two to have children, and it doesn't matter if Kate still gets shot, no babies will be in danger, and no worries about straining Beckett's heart. This is also why I have to pull back on Erika's age, because otherwise she'd be too old to have children with Beckett.
And that's it. I've had most of the first idea for a few days now, but the second one I only started building on earlier today. No idea what prompted it (other than a large number of baby fics I've apparently been reading today).