I strongly recommend you don't use any TTS at all. If I want TTS I can do it myself. I have no need of an app to do it for me.
That said, with actual human readers this could go very well. I would like, though, to point out the possibly insurmountable issue that pops up every time someone has an idea like this: copyright.
It is a sad state the current copyright laws are in, and a good example of that is how they interfere with the creation of awesome services like this one. IANAL, and all that, but I strongly suspect you'd get hammered down hard if you didn't get explicit permission from the authors of every single article you broadcast.
So seriously, speak with a lawyer, please, before taking a single step with this. Perhaps you can find a workaround, or someway to do this regardless. Or maybe not. But at least you won't drown under a mass of lawsuits.