Eh, that's not how it works. Web engines do a great job at providing accessibility for basic stuff, but to make an application and its content fully accessible,

Eh, that's not how it works. Web engines do a great job at providing accessibility for basic stuff, but to make an application and its content fully accessible, you would need to have accessibility as a requirement from the very beginning, make sure every little UI element is accessible (sometimes meaning provide additional fallback content), and constantly test your UI, which is never something that can be automatically added on top of an existing non-accessible UI.