@Jasper I must confess that thick as I am, I am still not entirely lucid on what exactly you are trying to clarify and why this is so important to you. Is it just that you wish these sentences to fit in with some neat boxed-up grammatical terminology?
BTW are you familiar with German or any other languages besides English?

@Jasper To my mind, there is a difference in the usage of "am" in the following:

A) Who am I to judge?
B) Whom am I to judge?

In A "am" is a true copula.

In B "am" is a sort of modal auxiliary: the verb "be" plus infinitive conveys something like "must", "have to", "should"; much used in business and military as in "All employees are to submit timesheets by Monday 0900 at the latest."

@HS Thank you for reaching out to us in your hour of need. As you now know, we operate an outreach program for those whom the modern vernacular has left feeling bewildered, betrayed and benighted.

There is a list of copula verbs here:

http://en.wikipedia.org/wiki/List_of_English_copulae

Right now I cannot see how to follow any of these with a complement and then an infinitive.

It is perfectly true that in English we often come across an infinitive preceded by an object pronoun which seems to act as the subject of the infinitive: I want him to come, I persuaded him to come, I warned him not to come, I wish him to come.

Quite how English acquired this type of construction I know not (although there is something similar in Latin, other Euro languages tend to say "I want that she go" - je veux qu'elle aille). English just seems quirky here and the structure varies from one verb to the next.

But with a copula???

Victoria: I am to be queen then?
Lord Melbourne: Yes, you are, ma'am.
Victoria: And who is Prince Albert to be? Who is he to be?
Lord Melbourne: He is in no way to be KIng, ma'am.
Victoria: Well, if it is not to be him, who is it to be?
Lord Melbourne: No-one, ma'am.
Prince Albert: Well, if I am not to be him, who am I to be?
Lord Melbourne: You will be the Royal Consort sir.
Prince Albert: The Royal What???

Like that?

http://books.google.com/ngrams/graph?content=It+is+me+who+*&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t2%3B%2CIt%20is%20me%20who%20*%3B%2Cc0%3B%2Cs0%3B%3BIt%20is%20me%20who%20is%3B%2Cc0%3B%3BIt%20is%20me%20who%20has%3B%2Cc0%3B%3BIt%20is%20me%20who%20will%3B%2Cc0

https://books.google.com/ngrams/graph?content=It+is+me+who+*&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t2%3B%2CIt%20is%20me%20who%20*%3B%2Cc0%3B%2Cs0%3B%3BIt%20is%20me%20who%20is%3B%2Cc0%3B%3BIt%20is%20me%20who%20has%3B%2Cc0%3B%3BIt%20is%20me%20who%20will%3B%2Cc0

Once we move to the more idiomatic "It is me.." , then "who" follows not the first person, but is treated as third, so the verb agrees with that.

http://books.google.com/ngrams/graph?content=It+is+me+who+has%2Cit+is+me+who+have%2CIt+is+I+who+have%2CIt+is+I+who+has&case_insensitive=on&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t4%3B%2CIt%20is%20me%20who%20has%3B%2Cc0%3B%2Cs0%3B%3Bit%20is%20me%20who%20has%3B%2Cc0%3B%3BIt%20is%20me%20who%20has%3B%2Cc0%3B.t4%3B%2CIt%20is%20I%20who%20have%3B%2Cc0%3B%2Cs0%3B%3Bit%20is%20I%20who%20have%3B%2Cc0%3B%3BIt%20is%20I%20who%20have%3B%2Cc0%3B.t4%3B%2CIt%20is%20I%20who%20has%3B%2Cc0%3B%2Cs0%3B%3Bit%20is%20I%20who%20has%3B%2Cc0%3B%3BIt%20is%20I%20who%20has%3B%2Cc0

@Jasper In my days we were taught that the complement is in the nominative case, and that "who" takes on the person of its antecedent; thus "It is I who am ....". Influenced by Latinate grammarians I think.
In books, the "It is I who am.." still outnumbers the rest by at least 6:1; although this may not be the case in speaking at all.

http://books.google.com/ngrams/graph?content=It+is+me+who+is%2Cit+is+me+who+am%2CIt+is+I+who+am%2CIt+is+I+who+is&case_insensitive=on&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t4%3B%2CIt%20is%20me%20who%20is%3B%2Cc0%3B%2Cs0%3B%3Bit%20is%20me%20who%20is%3B%2Cc0%3B%3BIt%20is%20me%20who%20is%3B%2Cc0%3B.t4%3B%2CIt%20is%20I%20who%20am%3B%2Cc0%3B%2Cs0%3B%3Bit%20is%20I%20who%20am%3B%2Cc0%3B%3BIt%20is%20I%20who%20am%3B%2Cc0%3B.t4%3B%2CIt%20is%20I%20who%20is%3B%2Cc0%3B%2Cs0%3B%3Bit%20is%20I%20who%20is%3B%2Cc0%3B%3BIt%20is%20I%20who%20is%3B%2Cc0

@Anwulf the subwait area is often just a few chairs in the corridor outside the doctor's room, like a forward waiting area, which saves the doctor wasting time trudging back to reception to find the next patient. I haven't seen it used outside medical contexts, although it is much the same in outlook as "gate lounge" at an airport.