Bushcraft knives seem to be a highly personal choice that varies based on what actual tasks someone will be doing with their knives when "bushcrafting" and where they live.
Some are happy with a small fixed blade like a Mora to simply carve, set traps, cut rope, and prepare meals. Others want a massive tank of a knife like a BK9 or larger that they can chop down small trees with and baton through 6" logs without risk of damaging their blade.
For backpacking where I'll be building only small fires with wood no larger than my wrist size, I like a 4.5-5.5" blade for wood prep. I do baton wood for fires but only if thats the only way to get to dry wood, otherwise I just find small sticks and tinder to start the fires with. Honestly, on most established backpacking trails, my 5" fixed blade isn't necessary unless I'm on a wet winter hike but I like to have it for fire prep and carving.
Here is a thread that may help you see what others are using successfully and give you a starting point to talk to your friend about ideas:
http://bushcraftusa.com/forum/showthread.php?t=61484