My DD was breech and also needed to wear the brace. Although, my case is a little different. She wore it 24/7 (except bath time) from the time she was 3 days old to 8 weeks so I can't really comment on if it will impede development stages. I can tell you she is now 6 months and totally fine. Just like any other kid her age and my doc says there's no reason she'll be any different or need special treatment. We should just be glad that the docs caught this in the early stages as when kids get older, it's a lot harder to correct. I would bring up your concerns with your doctor. Maybe they have some ideas of how to help your daughter reach those milestones.
Yes, it's tough to see your baby in anything other than those cute little outfits we buy them, but in the long run, this time will be just a little blip on the radar screen. Worse part, diaper changes. Urgh, those were a pain.
Good luck and remember, this too will pass.