Pulling an baby down the isle of an couple with an baby is not an idea that's unique. I have seen this in many TV shows and movies. Just because you said this first, does not mean your sister did not see the idea some where else like an TV show or movie.
I have seen this done many times for years on TV shows and movies and at real people weddings. You do not. It's her wedding.
It's been done many of time. Just because you want to do something does not mean your sister can not. Let it go.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.