I think you are off the mark on a few points.

First, it’s not even clear that this is Baby Doll’s imagination, by the end of the movie I think it’s far more likely that it was Sweet Pea’s. But that’s beside the point.

Seriously though, who cares where she gets her awesome powers or why they wear cool clothes while they fight zombie-steampunk-germans with a mecha in WWI trenches. I mean, look at that sentence. If you want to find anachronism this isn’t the movie for you. It’s heavily influenced by anime and no one ever wasted time complaining that elements of Sailor Moon or Pokemon don’t make sense. Beyond that though, it’s imagination. Comparing it to a full on fantasy narrative like Narnia or Harry Potter isn’t fair at all. Sucker Punch comes out and admits that the fantasy is someone’s imagination coping and not some alternate reality with rules of physics.

Finally, it was no where near as mind-bending as Inception. It seemed pretty clear to me when and where they were at all times.

This movie was terrible, no argument there.
But there where a few things that were very interesting.
For instance the fact that Baby Doll is not the center of the story
while being it, in my eyes she is the angel they talk so much about.
Other interesting thing is that she dying was the only way of resolving her conflict and that Rocket sacrificing her life was also the only plausible way
of resolving her conflict.
Overall it was a bad,bad,terrible movie, but that was cool.

Ps: sorry, my english is my second laguage.