As I wanted to avoid that, I decided to make the following changes to Shot 12 in particular;
1. Instead of flying through multiple eras with different design choices, the Falcon flies through a modern representation of London, stylised to look like graffiti.
2. Instead of animating separate characters like a smog skull, a spitfire and a pigeon, the Londoner's design would simply be taken and re-used on monotonous actions like stamping paper or walking down a street while the bird flies past.
3. Instead of animating the backgrounds by hand, I'd draw up about 3 or 4 backgrounds and move them around in after-effects.
I should have a rough storyboard for this new shot structure done by this evening so that I can start working on animating it next week.
In the meanwhile, here are some of the last few rough shots along with some animated segments from the original idea for Shot 12 before I decided to make the changes listed above.