Hip implants are not dangerous itselves but they usually move and produce discomfort (as far as I know). Anyway, usually doctors use very small implants (like 100cc or maybe 200cc) and they place them under the tensor fasciae latae, so i think they can't fix the hip indentation.
This is how they look (link is from a spanish plastic surgery center which performs this kind of procedures):
Usually best bet is filling the area with your own fat. I guess Carmen Carrera probably did this procedure since her hips and butt are really large... but she has no trace of fat anywhere else and her breast size is mostly due to implants.
Anyway, as other girls noted, having the perfect natural hourglass figure from the photo V posted is *really uncommon* even for cisgirls. Its not a matter of being born trans or cis, its a matter that girl just hit genetic lottery big time and actually she makes feel jealous most cis girls out there.
Quote from: V
Btw, Elodie, you're doing what I did... packing on weight after a few months of HRT. (I have to humbly disagree with Wednesday) It's smart, I think... I did this accidentally tho (didn't make a plan, I just put on pounds) and after losing the extra weight there I'm very happy with my shape now.
Don't do it humbly! I like to be changelled

Now seriously speaking I know it may work for some people but not for the most (I explained it before). As you said you packed weight unconsciously. That's another reason why advice against
gaining. HRT melts down muscle mass and slows metabolism, so if you mantain your weight pre-HRT you're already gonna trade muscle for fat, so I think there's no need to speed things up
Mod Edit:Removed Link