I agree with much that has been said.
You really need to showcase a few key things regarding Batman in order to get it right:
Bruce Wayne
Batman
Detective Skills
And the development into all that, which is something near impossible to do properly with Films and Movies that come out every few years
Personally, assuming WB are thinking like I am (and most likely not), you want this new Batman to be younger definitely, but showcase the Detective Skills portion, and the slow decent into what we encountered with Affleck during Batman v Superman (or something close enough to that to tie them all together; someone who has lost their way of being a "hero" and just stayed a vigilante instead as all he faced were crazy lunatics; like the Joker). But I'd also personally keep Affleck arround for current time Batman and Justice League until they can do a Flashpoint soft reset of some kind. Have the best of all worlds.
Regarding Robert Pattinson, I don't mind the guy, it's just there's something "off" about their face that I don't like (think it's the lips). Seems more villain than any sort of "dark" hero. Not only that, as mentioned by others, somewhat scrawny (Another reason why I'd rather keep Affleck around until a changeover happens, but back to topic, scrawny ala Zachery Levi in size and frame so needing a suit). If they put him with any of the other leaguers in the same scene, he's going to look REALLY out of place (either suit looks terrible, or looks tiny compared to others). There's only so much padded suits can help if the rest of you isn't up to par. And of course, I don't see Pattinson being the type to train up an acceptable size, and largely maintain it for many years as the others have done.
In short, you need someone for the long haul (prepared to stick around), or someone willing to go long haul that is. And I don't think Pattinson is that person unfortunately. Henry, despite all the controversy over contracts or what have you, at least is interested in the role of Superman. Pattinson, having the Twilight stuff behind him, doesn't seem like the type to stick around after at most 3 films.