Carice van Houten? We'd have to make her blonde, of course, but I can see her as older Galadriel. Or as some sage female elf figure at the very least; she definitely has that aura.
Really? I think it would depend on how much story we give one vs. the other. I think two actresses could definitely work in Galadriel's case. We already have grown Galadriel in the frame; using the same face for the main story as well may lessen that distant 'long ago' impact of that story. Or it would connect it in a nice full circle kind of way... she is an immortal ageless elf after all...but it would be nice to see a much more (visibly) youthful Galadriel for a change. I do agree, though, that if we were to use one actress Debicki would probably be able to pull both looks off successfully. I'm just not sure why casting different actresses would cause much of a problem.I think we should avoid casting two different actors as one elf.