iOS7 much worse for vision impaired users

Despite my warnings my wife upgraded her iPhone 4S to iOS7. She is vision impaired from both diabetes and chemo treatments. While parts of iOS6 were hard for her to see the new skinny Helvetica fonts and pastel coloration in iOS7 make it impossible to read even simple UI features like the phone keypad. Who at Apple thought that dark grey text on a light grey background would be readable by most people past the age of 40? I've tried all of the Accessibility features and while the Bold Text option does help a bit it doesn't do anything for text labels in graphical elements like the keypad or keyboard.

The Accessibility option to Invert Colors does help some of the pastel coloration obfuscations but it is stupidly also applied to your photos making the phone camera difficult to use and photos impossible to view. I have to wonder if anyone in Apple's phone test groups has anything other than 20/20 vision or is older than 30.

My options now are to either try reverting her iPhone back to iOS6 or to move her to out of Apple's walled garden to Android where she can get a bigger screen, replaceable system UI elements like keyboards, and viable accessibility options.

I'd love to see (and contribute to) a review of what mobile tech is actually usable by both the vision-impaired members of the public and even older techies like me who don't want to have to find a pair of reading glasses just to read a simple notification.