This seems to be a kinda... strange concern? I'm sure they'll make sure that the model fits the bigger races, but they probably wont re-design the whole thing, so the dress wont look like it was designed for a male Hrothgar. If that ends up looking "not good" to you, then dont wear it if you're playing a male Hrothgar?

And I can actually imagine a Roe or a Hrothgar wearing the wedding dress - it will look different than seeing it on a female Mi'qote, but thats kinda the point of playing a male Roe, isnt it? Looking different from a female Mi'qote.
Theres lots of gear in the game already that works better on certain race/gender-combinations, this will just be one more of them.