Yes, not mad, but very unfair to that kitten.
I don't want to sound patronising, i really don't, but you cannot begin to imagine how your life may be about to change. Some people have easy babies - feed every 2 hours, for half an hour, sleep between feeds to begin, wake every 2-3 hours at night for half an hour or so each time. Little crying, takes to feeding easily and only 8-10 nappy changes a day. Even with this you will be tired.
Dc1 was a tricky baby. He would not be put down at all in the daytime for over 6 months (yes, months), he napped on me, screamed in the buggy or car and woke every 45 mins for 5 months at night. A good night was when I had 4 hours broken sleep. I was tired beyond what you currently think is even survivable. And he cried so much, which broke my heart.
You cannot know what sort of baby you will get and IME you cannot influence it with routines etc. You just have to suck it up. If you are lucky enough to instantly bond with your baby you will care about very little else for a while, the love is phenomenal.
A kitten will require attention. You will have days you won't even know if you've brushed your teeth let alone fed and played with a new kitten.
I love cats. Our own died sadly when dc2 was just 5 weeks old. She was a much easier baby but there was no question of having a new kitten until dd is older.
IMHO it would be unkind to the kitten to do this until you know what you're facing. I'm sure the breeder will breed her again at a later stage?
Good luck with the end of your pg and early motherhood OP, it's amazing.