In terms of staying historically accurate, we have no real evidence for draw weight, or bow length from this period. All we have are the Mary Rose bows from a hundred years later (roughly 100# to 150# draw weight and between 74" and 80" long) but I think at the moment most people are counting those bows as fairly good estimates for the 100 Years War bows.
Is your colleague actually attending the Agincourt 2015 event? If he is, he can use any weight bow he likes. I think most warbow archers will be taking a couple of bows - a heavy one for the distance/flight shoot and a much lighter one for shooting at the clankies.
As for making them - get in touch with some of the guys who are "topping the charts" so to speak with warbows - people like Ian Sturgess on here, or Ian Coote if you have Facebook. Both of them have made true warbow replicas that are setting global records for performance with military weight arrows, and are very generous and helpful if asked.
As a rough guide (and I'm just a novice so take this broadly) you want to be looking at a roughed out stave that's around 78" long. 40mm wide in the center, staying parallel for 20cm each side of center. Mark out the tip at just over 25mm wide, and taper from 40mm to the tips. Mark 35mm thick at the center and taper straight to the tips.
This gives you a solid and predictable shape to start tillering. Once it's bending fairly evenly you can reduce the tips - from about 10" from the tips, taper to just over 13mm wide. That gives you the classic and accepted profile of the Mary Rose bows and if the bow was bending nicely should bring the tips round better and start to look close to finished shape. The tiller shape can either be a perfect circle or for slightly better performance stiffer in the handle with gently whipped ends.
As I said I'm a novice but that's how I've been taught and I believe that's how the top bowyers make theirs.
Keep the sapwood thin, don't stay on the long string too much, brace as early as you can, drink lots of tea, get a stress ball, don't get yew from Medicine Bow Woods and you should be fine.