^Wesker can literally teleport all over the place, so nothing out of the ordinary at all. As for anyone asking, and you know this question would inevitably come up, "how can you be attacked by creatures that aren't real (since they're "hallucinogenic")?", well, you could say they're actually your typical zombies appearing more ghastly via said hallucinogens. And they could come from a hallucinogenic version of whatever virus created them, that would be an original idea that's never been done before in a RE game. A ship level (similar to Revelations) would be perfect for this type of zombie/BOW, it would literally be a ghost ship, LOL.
And the multi-headed hydra BOW could, in addition to severed limbs, have numerous mutated, distinct heads, and they would all be mutant heads, but very much inspired by mythological hydras (multi-headed dragons), they could all have long necks attaching them as well. That would look awesome if done right.