Well yeah but the effects of the poison would shut down your chakra network, so when you went to activate the technique wouldn't you just die? I guess that takes it back to the physical/non-physical body damage, but I feel like because of the fact it's a Curse, that if it didn't take effect before you activated the technique it would take effect after, wouldn't the technique be more of an "attacking the soul type thing" since it would deal the damage out to both users, I don't feel like turning in to fire would stop the technique, and yeah I get that you can't stab fire/water/rainbows/whatever but the way the technique works I feel like it would still kill you either way, the fact that it can be done without having to be anywhere near the person suggests spiritual connection in the Curse, so it's more of a both of your souls died type thing, It's not that the needle pricks would kill you or whatever, it's what the poison would do to Eikan would be reflected to you, the shutting down of the chakra system and dying, and since it would be done on more of a spiritual level, I don't think not having a physical body would avoid it, it would either like I said cause you die after deactivation of the technique, or just stop you mid technique and kill you.