Can I develop a custom screen reader instead of VoiceOver?

I am looking at developing a UI automation framework that would utilise the accessibility framework.

Target audience would be corporate testers, not the public.

The corporate tester would install the custom screen reader to their device, which would then perform the actions detailed in a script to test the UI.

Preferably without recompiling the target app, and also supporting native Apple apps.

Thanks,

Mike.