again like others said i really wouldnt want to waste a big big name guy for ben this go around as since we are skipping the origins we likely only see ben in a few scenes per film and they be dreams/visions/ or the occasional flashback we may see. So that is why i rather go a lesser name like michael j fox or nichalos hammond type. And a bigger name like tom hanks, greenwod, etc..... it would likely be more suited for them to be jonah then ben.
On michael speech i have see more recent stuff with him and he doesnt sound that bad. But still michael would be a fun choice for ben i say. But who ever ends up as ben i hope is cool too. Like i said before only thing i would be pissed on if we dont see ben at all. And his character is just used in refrence and a photo on a wall where we cant really get a good look at person.