What can Alucard actually do now?
The only powers he should have lost are the ones based on having other lives within him. He should still have the physical abilities of his Level Zero form, as well as his psychic abilities and some degree of shape shifting.
As for what abilities he
acquires from Schrödinger, in theory it should be everything. Schrödinger didn't have abilities per se, but rather it was his nature to exist in the quantum states of everywhere and nowhere. As long as he recognizes himself, he can choose a single one of these states to occupy.
The question that remains is "Can Schrödinger-Alucard come back from being vaporized?" and unfortunately the answer is not really clear. What it boils down to is "Can Alucard remain aware of himself if his body is destroyed?".
Schrödinger came back from getting his brains blown out, and Alucard has shown some neat shapeshifting, but he's never actually had his entire body destroyed. There's always some blood or chunks leftover.
One might claim that Alucard's 'brain' still works while gibbed or shape-shifted, but that it would not continue to work if he was totally destroyed by, say, a nuke. If that's the case, a nuke would be sufficient to prevent him from being self-aware and therefore unable to come back with the Schrödinger power.
The other theory would be that he (and Schrödinger) have a sort of higher order consciousness (or 'soul', if you like) which operates and thinks without a body. This is supported by
- the existence of souls, stored within Alucard and then summoned along with their bodies
- the fact that Schrödinger can come back after having his brain blown out despite having no shown regeneration or shapeshifting ability
- the fact that Alucard came back from not existing
If this is the case, killing him requires somehow stopping his soul from perceiving itself. The Major's tactic wouldn't work again, since Alucard probably isn't stupid enough to consume another bunch of souls.
