No, you cannot include such a clause. To comply with Australian employment law and the Fair Work Act 2009 (Cth) employees may apply for and receive compensation for a change in their employment in certain circumstances.
If a company makes a “significant change” to an employee’s role, then this may be considered to be a repudiation of their current agreement. In these circumstances the employee is not necessarily required to accept the change. If you make a “significant change” to an employee’s agreement the employee may have grounds to argue that this was a breach of contract, that the agreement is terminated, and they may have grounds to argue that they are entitled to redundancy pay.