How completely does the character become the mundane beast he transforms into? Is it in form only or do all the traits of the creature become dominant ?
p.48 and 67 of AM5 are not specific about how complete the transformation is.
When fighting as a Bear does the character use his human Brawl skill or that of an actual Bear? I would have thought he would use the Bear skills . . but from where has he learned them if he just spontaneously discovered that he could take the form of a Bear?
How much awareness of the characters humanity is retained in animal form? If total awareness is retained for the first few hours/days how soon would the animals nature take over until the memory of being a human is a vague one? If a character hibernated as a bear would he wake up after months of bear dreams confused or indifferent to his human form? How long before the memory of humanity is gone?
Lastly and slightly off topic:
If he has a Martial Ability Block flaw in human form does this impact his Brawl Ability in Animal form?
I know this is entirely unhelpful, but there is a continumn here. Some of the Norse magi wear bear shapes, literally, so that if you cut them deep enough you can see the human skin under the layers of bear muscle, and they retain their human faculties. On the far extreme other end are the mazzeru, who lack any control at all of what they do while in wolf form. Which is to say: ask your troupe and do what seems interesting to you. Any and all answers can be argued to be right, if you want them to be right.
HoH:MC - Bjornaer section goes into this. Use the bear's (physical) abilities. However, if the character spends enough time as a bear, you may allow the character to apply points to the bear abilities.
Technically, yes, flaws do carry over. So the bear would have Martial Ability Block.
I think it is somewhat odd that Brawl is not included in the Martial Ablity Block Flaw. Hand to hand combat with a knife is a Martial Skill is it not. Therfore it makes sense to include Brawl in the Block even if it is not strictly a Martial Ability.
IMHO, Brawl is seen as the simpliest way to fight, using fists, kicks or any simple weapon like knives or bludgeons, while the Martial Abilities cover the use of more "sofisticated" weapons. I think this is the main reason because it's a General Ability: because even a child or an animal can learn how to fight in that basic way, while Martial Abilities cover the use of weapons made for "war", a typical human activity, not a natural fighting style.
Consider this: every animal has the Brawl skill, even if it is a docile or a herbivore one. Why? For me it's because both predator and prey have an intuitive skill to catch/evade the attacks of their natural enemies.
Final tought: have you considered the Flaw Noncombatant for that character? IMHO, it's a better choice if you want a pacifist/fighting-incompetent character, expecially if combined with the Ability Block Flaw...