HaLevi: I guess you are talking about intangibility in your distinction between a ghost and Eliyahu Hanavi?
Are you suggesting that if someone sat in kisei shel Eliyahu, he would actually feel Eliyahu? I would guess that Eliyahu is visible and tangible to some while at the same time remaining invisible and intangible to those that aren’t zocheh.
Also, if Rebbe made kiddush he must have been able to hold the cup. I don’t he would make kiddush without holding the cup with all five fingers.
Personally, I think that without reaching some madreigah of kiddushah it would be impossible to see a neshamah. I recall seeing somewhere that Eliyahu Hanavi and malachim have to put on some type of body when coming into our world. It sounds counter-intuitive to me that a person who died would be given this levush too.