You could also try Australian Industry Group - Biz Assist line if you are already a member. You might want to try and highlight to the US parent company Section 343 and 344 (copied below for you) of the Fair Work Act which expressly relates to coercing people to sign IFA's or other types of agreements / arrangements. It's a tough situation for you to be in, so I would take it to the most senior person in Australia (assuming there is someone else you can go to here) and advise them of the enormous risk that this will put the company in (and the exposure to you under section345!

).
The options that are being offered are correct though, an employee can be paid above the Award, therefore no entitlement to penalties, allowances, leave loading etc, however the cotnracts should be very clear about what the salary covers. I've posted a question on here about "set off clauses" which is exactly what this relates to, ie wording about the fact that the "salary you are receiving is in full and final satisfaction of minimum salary, overtime, penalties, allowances and elave loading" etc. The other part of the clause that needs to be inserted is something along the lines of "should any Award change to provide you with any benefit,
X (comapny) will set that benfit off against your current pay, therefore absorbing the benefit into your salary without increasing the overall amount"
Or, they can with 28 days notice win writing, go back to Award entitlements, which could ultimately be less pay, but all of the previous payments that were included in their salary become payable.
343 Coercion
(1) A person must not organise or take, or threaten to organise or take,
any action against another person with intent to coerce the other
person, or a third person, to:
(a) exercise or not exercise, or propose to exercise or not
exercise, a workplace right; or
(b) exercise, or propose to exercise, a workplace right in a
particular way.
Note: This subsection is a civil remedy provision (see Part 4-1).
(2) Subsection (1) does not apply to protected industrial action.
344 Undue influence or pressure
An employer must not exert undue influence or undue pressure on
an employee in relation to a decision by the employee to:
(a) make, or not make, an agreement or arrangement under the
National Employment Standards; or
(b) make, or not make, an agreement or arrangement under a
term of a modern award or enterprise agreement that is
permitted to be included in the award or agreement under
subsection 55(2); or
(c) agree to, or terminate, an individual flexibility arrangement;
or
(d) accept a guarantee of annual earnings; or
(e) agree, or not agree, to a deduction from amounts payable to
the employee in relation to the performance of work.
Note: This section is a civil remedy provision (see Part 4-1).
345 Misrepresentations
(1) A person must not knowingly or recklessly make a false or
misleading representation about
:
(a) the workplace rights of another person; or
(b) the exercise, or the effect of the exercise, of a workplace right
by another person.
Note: This subsection is a civil remedy provision (see Part 4-1).
(2) Subsection (1) does not apply if the person to whom the
representation is made would not be expected to rely on it.