The only problem I can envisage with the first one is regarding GZDoom's dynamic lights. Perhaps in a case where an actor is partially lit by a dynamic light, some kind of average could be taken to determine the returned value?
I await your thoughts, and hopefully not an immediate [No].

EDIT: finding the sector tag would probably be better suited to a separate function like GetCurrentSector or whatever, as it doesn't make much sense in the context of actor properties. Hmm.
EDIT #2: changed 'TID' to 'tag'. I was drunk when I posted this.