>>1
What does your teacher mean by flaw, I wonder? I'd argue that the existence of a single irregular verb could be considered a flaw. I guess #7 above agrees with me.

Getting more specific on the gender arguments, I'd also consider the lack of a gender-neutral term for 'sibling' a flaw (albeit one that's shared with most languages).

Frankly, I think the whole concept of finding flaws in languages or identifying "perfect" languages is more than a little ridiculous--the arguments on both sides can't help but say more about nationalism or cultural chauvinism than they do about linguistics.