I struggle 4 hours with a late 2013 macbook pro installing windows 7, here is how I solved the problems I had.
I went through the whole bootcamp process, with the 3 options ticked as on this picture:
On the first reboot, I had the "bootmgr is missing".
I went back to bootcamp assistant, selected the last option to remove the partition and then rebooted holding ALT and selecting the first Windows drive (I had 2, I'm not sure why).
Once on the windows installation screen (select language), I had no mouse, trackpad or keyboad, stuck again.
I went back again to OSX, you need to go in the osx preferences and turn off bluethooth so that proper drivers will be downloaded by the bootcamp assistant. So do that before using the bootcamp assistant.
I went through again the whole bootcamp assistant process, with the 3 boxes ticked and I was finally able to boot on the install and I had a keyboard and mouse to continue.
Hope that helps.