This is totally cool, and I can totally see She-Ra kicking a huge horde giant's butt and saying that exact line to it! What an amazing work of art... and I can totally picture this being done in a 300-style graphic novel too, that's what's so awesome about it.
I think being tough in a skirt keeps the feminism feminine. I think a strong (physically or otherwise) female character doesn't need to wear a manly outfit. I think that hurts feminism if women are expected to dress like men or deny their femininity to appear "equal."
And as you pointed out, He-Man wasn't wearing pants. Or more to the point, it's not like we have fully armored men and chain mail bikinis. Both genders show skin, and the outfits (male or female) don't come off as gratuitously revealing.
I watched the entire animated TV series again, but this scene I could not find For the Honor of Grayskull. Who is mightier than SHE-RA? You are, 'cause you have the power to let her do this wonderful feats of strength