I love the potion that you came up with. It's really kind of funny how it needs to have the blood of his father... that must be a death eatter. So wonderful that they have both. I find that makes me smile! Oh and Snape's comments earlier in the chapter... His sarcasm- that was great too!

About your question, to bring Lily back. That depends on how you do it. Like you said, the "never died" and "back from the dead" seems like and obvious no. But I bet your "in a sense" could really come out nicely. Perhaps your Lily's room, with the light magic could be of use (maybe you're heading in that direction already). Like they can restore the room and maybe some of her essance is saved, a bit of her spirit... and they can talk to her there, like as a ghost, but not a ghost...hhhmmm a memory. Something that couldn't leave the room...