Hm...if Aberforth were really occupying Snape's body, would the marauder's map see him as AD or as Snape? I think that would totally be up to JKR. As we've seen, it wouldn't work with polyjuice, but if there were a way to transfere somebody's mind into another man's body, it would not be a copy, but the real Snape's body.
Do animals show up on the MM? To me, it seems as if in HP, animals had nothing like a soul or something, and if they showed up, it would be a definite sign that the MM shows bodies, not souls. So, unless Mrs Norris is an animagus, it would show Snape, as it is his body, not AD.
I dunno...did I get across what I mean?