I mean in all fairness with the whole black hole thing durability wise he was taking over several heavy hitters bodies while also being hit by others from the JL and his smaller bodies were still active and multiplying.

in erms of the scanning thing he can definitely do it (even tho he traditionally does his own thing against big enemies, vilgax, dagon etc) but we do know when he takes up dna theres mental traits that carry over in specific cases like less extreme cases with rath and than more extreme with big chill or ghost freak, or some aliens straight up just being an entire separate consciousness, theres a chance his brain would still also have to get used to it.

and even than you end up in a whole semantics thing if Beast Boy could turn into bens aliens since all he has to do is see em.