Well it compiles; just synthtissue and TongueLoss now.

code/modules/antagonists/changeling/changeling.dm

@@ -340,7 +340,7 @@
 	if(istype(C))
 		var/obj/item/organ/brain/B = C.getorganslot(ORGAN_SLOT_BRAIN)
 		if(B)
-			B.vital = FALSE
+			B.organ_flags &= ~ORGAN_VITAL
 			B.decoy_override = TRUE
 	update_changeling_icons_added()
 	return

code/modules/antagonists/changeling/powers/regenerate.dm

@@ -35,7 +35,7 @@
 				B = new C.dna.species.mutant_brain()
 			else
 				B = new()
-			B.vital = FALSE
+			B.organ_flags &= ~ORGAN_VITAL
 			B.decoy_override = TRUE
 			B.Insert(C)
 	if(ishuman(user))