The clerk has just brought to my attention here a draft clause. Let me read it out, because I think it may capture what you're trying to achieve.
In the case of previously scheduled meetings taking place outside the parliamentary precinct, the committee members in attendance shall only be required to wait for 15 minutes following the designated start of the meeting before they may proceed to hear witnesses and receive evidence, regardless of whether opposition or government members are present.
Is that what you had in mind?