Can a medium character take the exotic weapon proficiency to weild a small weapon without penalty? Meaning could my half-elf magus use ancestral arms to take the ewp feat for "small elven curve blade" and thus weild it one handed? I know it would be a die step lower, but the 18-20 crit range d8 weapon, that can be used with one hand is hard to pass up. I know I would not gain the proficiency for the standard sized Elven curve blade by doing this, but is it technically legal?
Can a medium character take the exotic weapon proficiency to weild a small weapon without penalty? Meaning could my half-elf magus use ancestral arms to take the ewp feat for "small elven curve blade" and thus weild it one handed? I know it would be a die step lower, but the 18-20 crit range d8 weapon, that can be used with one hand is hard to pass up. I know I would not gain the proficiency for the standard sized Elven curve blade by doing this, but is it technically legal?
Nope. EWP gives you proficency with a weapon regardless of size, and does nothing to affect size modifiers. As a house rule, I think it's perfectly reasonable, though.