The Pressure on Children:
Compulsory Toxic Masculinity, Femininity, Gender, and Heterosexuality etc.
From birth, toys are separated by gender. Cisgender/straight/able-bodied/neurotypical white men are seen as the "default" human beings that society revolves around; everyone else is seen as a lesser alternative. And if you are not cisgender, straight, or white, forget about seeing yourself in toys. There are kids who are neither boys or girls, or don't fit in the binary.
It is important to not let gender dictate play; play is crucial in a child's development and helps shape their worldview and relations to others.
To be a girl, a child must perform femininity and see their value only in unattainable white-standard beauty, they cannot play rough, and they must reserve their emotions for performing labor for others. Dreaming big means finally seeing "Doctor Barbie" created, while boys have had career toys and every other genre of toy (sci-fi, etc.) available the entire time.
To be a boy, one must repress all emotions except anger and entitlement, because that's power. Boys live out violence and colonialism through G.I. Joe and Transformers. A male-dominated society creates emotionally volatile and incompetent men that thrive on their privilege and harbor abusive relationships, starting in these childhood experiences. The onesie shows that heterosexuality is imposed on literal infants.
Usually the only toy options that are untainted by this is open-ended play, like blocks.
In popular franchises there will be only one girl, maybe two. She will be skimpily clad, over sexualized, white, conventionally attractive, and fail the "sexy lamp" and "Bechdel" tests, etc. And she will be cool because she "is not like other girls", meaning she isn't feminine. Our double standard is that girls need to perform femininity, but then femininity is seen as weakness.
If there need to be promotional storylines or media for the toy, they will revolve around exploration, friendship, kindness, and positive qualities that foster healthy environments, growth, and wellbeing.
Expansion packs can provide new parts for further mix-and-match. There won't be any weapons, just cool technology with different skills like exploration (space, water, forests...) Other packs can promote art, reading, environmentalism, animals, etc.
Expansion packs can show how the things around us are special and fun to learn about.