Adding or subtracting a character in the middle of creating a lengthy work is nearly as challenging as breaking up with a longtime life-entangled partner.
Draw on the best of the way the world is and has been, as well as your most optimistic hopes for what it could be. The real world is very unfair to those on the margins. Use your writing to make up for it.
You're operating by improv theater rules, where as soon as a character introduces a new idea, you say "yes, and" to it. But this theater troupe answers to your direction.
The question underneath your question is: "Am I allowed as a commercial writer to do the thing I want to do as an artist?"
We're swimming in the narrative conceit that what makes extraordinary characters interesting is their extraordinariness and what makes protagonists interesting is that they're protagonists.
Lots of things happen that characters don't know about, or only hear about. That's part of life, and is perfectly fine to include in fiction. Instead of trying to fix it, have your characters react to it.
If you still want to write even after you let go of any feelings of being obligated to write, take some time to think about why. Are there ways to access those motivations and keep them in the front of your mind so you can gain some satisfaction and joy from them?
Today is the fifth Tuesday of the month, which means that my answer to this heartfelt letter is available exclusively to my Patreon patrons.
Since your circumstances make writing a bit challenging for you, you're responding to that by sitting squarely in your comfort zone. Every writer does this from time to time, especially when starting out, and there's no shame in it. You just need to recognize that it's what you're doing, and consciously make the decision to make yourself uncomfortable in the service of your art.
Books often change quite a lot as you're writing them and the book you've written may require a somewhat different protagonist than was called for in your original outline.