Anderson is a perfect MMA middlewieght; his body and mind obviously respond about as well as anyone's can to that particular cut, and he enjoys an advantage in speed over most of the other guys in that division.
I have no idea what he would look like at HW, but I have to suspect he would be slower, his strikes wouldn't have the same effect, and he wouldn't be as powerful as the majority of the fighters up there.
Until I see him actually in the octagon at HW, I'm simply going to say AS at HW is unpossible, so the OP becomes mute.
Finally, someone on this post that isn't a Silva fan boy, posting realistic comments. Yes, I agree Silva is the P4P best, very few even come close. But to say he'd run thru the HW class is ludicrous, he would do great at LHW and probably end up holding that belt as well, no way does he do the same at HW. First he'd have to put on weight, which would be mostly chub, (he's pretty doughy as it is)as he doesn't have a tremendous amount of muscle to begin with and that will slow him down and would also effect his gas tank. If he were to move to HW, the only people that he could stand a chance of beating is guys like Pat Barry (sorry Pat, I'm a big fan but it is what it is). Put him against JDS and he'd be dead meat in the 1st round.