This is from the newly signed Australia - Indonesia CEPA:
Article 20.8: Establishment and Reconvening of Panels
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3. Within five days of the date of the receipt of a request under Article 20.7, the Parties shall enter into consultations with a view to reaching agreement on the procedures for composing the panel, taking into account the factual, technical and legal circumstances of the dispute. Any procedures for composing the panel which are agreed under this paragraph shall be used for the composition of the panel and shall also be used for the purposes of paragraphs 12 and 13.
4. If the Parties are unable to reach agreement on the procedures for composing the panel within 15 days of the date of the receipt of the request referred to in paragraph 3, either Party may, at any time thereafter, notify the other Party that it wishes to use the procedures set forth in paragraphs 5 through 7. Where such a notification is made, the panel shall be composed in accordance with paragraphs 5 through 7.
5. The Complaining Party shall appoint one panellist within 10 days of the date of the receipt of the notification referred to in paragraph 4. The Responding Party shall appoint one panellist within 20 days of the date of the receipt of the notification referred to in paragraph 4.
6. Following the appointment of the panellists in accordance with paragraph 5, the Parties shall agree on the appointment of the third panellist who shall serve as the chair of the panel. To assist in reaching this agreement, a Party may provide to the other Party a list of up to three nominees for appointment as the chair of the panel.
7. If any of the three panellists have not been appointed within 45 days of the date of the receipt of the notification referred to in paragraph 4, either Party may request the Director-General of the WTO to make the remaining appointments within a further period of 15 days. Any lists of nominees which were provided under paragraph 6 shall also be provided to the Director-General of the WTO and may be used in making the required appointments. In the event that the Director-General of the WTO is a natural person of a Party, the Deputy Director-General or the officer next in seniority who is not a natural person of a Party shall be requested to make the required appointments.
There are a number of possible variations on this approach, but in my view this is the basic model everyone should use in FTAs going forward.