It's fun to meme about engineering a waifu, and certainly in ancap without all those pesky restrictions it would be easy to make one, but what about the ethical implications? Since ownership of a sapient creature violates their NAP, how do you plan to get around this? The only things I can think are
1) Making them not actually sapient which isnt so fun
2) Not actually owning them and having to engineer them and then woo them which sounds like trouble