No, not every loli is designed to be lusted after, but they are then designed as a figure for the otaku to feel protective of, to be a "white knight" for, or an "older brother" which is in itself a sort of fetish, nonsexual. These characters are overprevalent in anime, and that is the thing I hate secondmost about anime these days. The first is just how restricted most anime is to japanese culture. Even anime/manga set in a western setting is drenched in japanese ideals and cultural norms, because it is meant to appeal to a japanese fanbase. I'm not saying there's anything wrong with that, or that other cultures don't do the same thing with their works, but I just don't care for it. I also find that work coming out of other, western cultures is more internationally accessible, but that's just me.
And I really don't care what the age of consent in Japan is. A 30-odd year old man lusting after a 13 year old is wrong in any country.
To me, there is no dichotomy in a child wielding some kind of huge weapon or whatnot, because such media is saturated with those types of characters now (eastern and western, though moreso eastern- see Hit Girl from the comic/movie Kick-Ass). It's not surprising nor shocking, and just doesn't seem special to me. It's gotten tired for me.
@veekie
I don't think the cohort granted by the Mentor feat is really meant to follow you around. I'm not really sure what level it would be or anything.
I guess reading further, an Apprentice doesn't follow you around, but once they in turn graduate apprenticeship, they may follow the mentor as a cohort, so I guess there's that.