OP....if you have experience riding in pacelines, another strategy would be to ride a very early wave, say 5:30 pm start on Sunday and latch onto fast groups and ride right to Brest arriving in under 30 hours. Sleep there and then again for 8 hours halfway back. You have to be able to climb fairly well.
To repeat my suggestion in more detail. Do a few 200K this spring and focus on skills and logistics for efficiency. Then, do a 300K. I would treat the 400k as a final exam of your logistical and efficiency. If you can finish a moderately hilly 400k in around 20 hours with less than 90 minutes stopped, you have an outside chance at getting the sleep you require. If you can do a moderately hilly 400K in under 18 hours, I am sure you could meet your goal if you can manage the controls. If it takes 21-25 hours to do the 400k as it does many randonneurs, you won't get a ton of sleep on a 1200k. If you decide to go beyond 400k, try to get a 1000k under your belt before PBP. I failed my first PBP and had done two SR series and much more in prep, my failure was due to my stupidity. After 200-300K, it is all mental and some of that is knowing what not to do. Most people like me have to learn this the hard way by experience. You need to get that experience......this year. PBP is not easy.