it sounds like you're putting a lot of work into this but there are a lot of things about the rules/world that can't be changed and at the same time be called baldur's gate.

the only alignment restrictions in place now, for example, are as follows...according to the D&D rules, i mean

Bard: non-lawful
Barbarian: non-lawful
Druid: first part of alignment must be neutral
Monk: first part of alignment must be lawful
Paladin: must be lawful good

all others can be of any alignment and take no penalty if it changes

EDIT- what yocko said too...also, vampire is a template that can be added to any humanoid (human, elf, etc.) or like creature...including giants and monstrous humanoids like minotaurs, etc