well, in all cases, the relex dependencies are arrows, pointing from the head to the dependent.  So ordering always matters. For _amod, the head is the noun, the modifier is the dependent. So:

The tall woman is a registered nurse.
    _subj(be, woman)
    _obj(be, nurse)
    _amod(woman, tall)
    _amod(nurse, registered)

So, OK, by analogy, who(woman, live) seems just about right, if you want just shallow structure.

The deep structure is "A woman is a nurse. A woman lives next door. Both women are the same woman". The syntactic function of "who" is to act as a subject for the dependent sentence, since the English language prohibits null-subjects in many/most cases.  "who" is the not-quite-null subject for "lives next door".  (See http://en.wikipedia.org/wiki/Null-subject_language)  

At the semantic level, "who" refers back to "woman", and that's how we know there's just one woman, not two in this sentence.

The simple, surface parse would yield   _subj(live, who)  but that is not being generated. Instead, the above shows  _subj(live, woman),  -- there are now two sentences (since there are two subjects) and there's an ambiguity: is it the same woman in both sentences?   That's why I suggested who(be, live):  it connects the two sentences back into on sentence. 

Compare this to the simpler situation: "A woman lives next door, she is a nurse".  This generates:


    _advmod(live, next_door)
    _subj(live, woman)
    _subj(be, she)
    _obj(be, nurse)

There's no relation showing that "she" is the same person as the nurse. We have the semi-functional Hobbs algo to provide this, but its got issues.    Then there's the sentence:  "A woman lives next door, who is a nurse." which currently generates:

    _advmod(live, next_door)
    _subj(live, woman)
    _subj(be, _$qVar)
    _obj(be, nurse)

which is wrong. If instead it was  _subj(be, who) instead of _subj(be, _$qVar) we would still be missing the connection that "who" is the woman.

Inventing three different mechanisms to indicate "who", "she" and "woman" are all the same person is .. confusing.   More generally, relex does a mixture of shallow and deep analysis, and its schizophrenic about that: is it picking out deep structure, or shallow structure, or both?