So when a warforged Pale Master goes into wraith or lich form, they go from construct type/living construct subtype to undead type/??? subtype.
Any thoughts on what the new subtype is?
Pen and Paper has no rule for this, since in PnP warforged, nor any constructs for that matter, cannot become undead. But Turbine has decided to bring in a house rule for that, and I am merely pointing out that the house rule is incomplete. How they decide to complete it is relevant because it will decide whether or not warforged can be repaired in undead form.
If they are supposed to be undead/un-living construct, then they should still be able to be repaired since repair spells are transmutation and have nothing to do with the polarization of the life force attached to the target in question. In fact repair spells work just fine on non-living constructs (ie golems) who have no life force whatsoever.