Here's a GM's reply to the players point of view.

Topic 1: I would say that there would be many rumors from all over the
world with many names mentioned but no details. My impression from the
Blood Enemies book was that the Abominations where shrouded in mystery
and vauge rumors of horrible power. So while names may be known details
would not, I also feel that while a player might know the Abominations
from his region, ie Anuire, he wouldn't know about the Magian over in
the Kinashi lands unless an Kinashi told him about it.

Topic 2: As long as this was done with the understanding that level
alingment and class were "apperant" based on previous actions and
behavior this would be a good idea.

Topic 3: In battle I agree its not evil and maybe Bloodtheft is a
misnomer for the act in all cases. HIGHLANDER does have some good
Birthright aspects to it so those are good points for us to consider.

Topic 4: What happens after killing a scion of Axari isn't a penalty.
The bloodline change is a simple act of mystical physics for lack of a
better phrase. As I read LotHK becoming the blood of Azari doesn't
instently make you evil it simply make you have more evil thoughts and
have to deal with more temptation. In the original boxed set there is a
paladin with Azari's bloodline so its possible to still be good you just
have to work harder.

I could be off base about some of this but those are my views on the
things KirbyRanma mentioned.