Overall, the high-level information you provide in this post is generally good. Normally I would ding anybody for using Medium when writing about accessibility, owing to its complete lack of support for alternative text on images, but I understand you are still learning about accessibility and its impact.
In this case, I would encourage you to make your captions more descriptive since right now they are not adequately conveying what is in the image. That is a step you can take today to mitigate one of Medium’s built-in limitations.
But then I got to point number six: Accessibility Toggle
There is almost no scenario where this is needed. Building screens that validate means in almost all cases this is unnecessary. There are sometimes special cases, such as a drag-and-drop interface for example, where an alternate method may be made available, but that should be an exception.
Things to consider with an “accessibility toggle”: Not all users consider themselves disabled in any way; the user experience often suffers as that becomes a separate but unequal set of screens; those screens / features are often not updated at the same pace as the primary interface; support reps rarely understand these features and cannot help users effectively; extra effort is being squandered when just building a proper interface would be more effective; it treats disabilities as a problem requiring duplicative effort, which is not true; you miss the opportunity to get your core team familiar with building inclusive components; and so on.
In short, an accessibility toggle is (from experience) a poor solution to a perceived problem that is best addressed with good development and testing practices instead.
I encourage your readers to look at some free online materials around accessibility, such as this free course on Udacity from Google: https://www.udacity.com/course/web-accessibility--ud891
Since I am here, I noticed something else unrelated to the topic of this post, primarily around where you sourced your photos.
Crediting images as “courtesy Google” seems odd, since Google cannot grant permission to use images that are not Google’s. Just grabbing the first two images of your article, the curb cut is from Virgina Department of Transportation (http://www.virginiadot.org/projects/northernvirginia/ada_sidewalk_ramps.asp) and the door opener is from a company that makes them, Access & Mobility (http://accessandmobilityinc.com/our-products/power-door-openers/). If anything, it looks like you have taken these images without permission.