New prestige class

[PCyric]

Lord Eldred, in that case you definitely do not have to grab their heritage. Thus you do not need to be e bloodhunter. You could just try to kill them, in order to be rid of him, or destroy his tie with his bloodpower (something like suppress blood line, destroy bloodline etc). If you are a bloodhunter and you only search for those who use their heritage to harm others, you won't have the greater chances on blood theft (since you do not grab the blood powers, you just destroy them, with various means). In that case you could enven be LG in alignment.
It's all about motivation and what you hope to gain each time you do something...

[Arch-Sorcerer Gargamel]

Are we talking values here? In the warrior society of the time, honorable combat was simply combat in which both members were able fight to the best of their ability and aware of the terms. The purposes for invoking may be good or evil, depending on the aggressor, however, the act itself would have been considered merely lawful and (somewhat) divine.

A bloodhunter could be someone who has just devoted themselves to the intricacies of slaying scions. An evil one may be a ruthless murderer and a good one may be a justice-seeking vigilante. In either way, the idea seems like a good one. New abilities (such as increased gain) regarding bloodtheft may be a side-effect of this single-minded devotion to blood knowledge.