I want to make something absolutely clear about what I think regarding authority within Liber XV. Disclaimer: I am an ordained Priest, but I am not a Bishop. That said, the framework of my opinions has been accepted as accurate by my own supervising Bishop, as well as others.
The authority to celebrate the Gnostic Mass is embodied in the officers, namely the Priest and the Priestess. That authority derives from either being an ordained Bishop, or from acting under the direct, formal supervision of a Bishop. The Bishop's authority comes from the national Primate. His authority comes from the Patriarch of the E.G.C. There is no other authority when it comes to any discrete celebration of the Mass---not the community, not the Lodge Master, not other Bishops (except, for the latter two, insofar as they feel compelled to enforce Grand Lodge policy and in the rare occasion when the sanctity of the local body is endangered, say with the presence of a 15-year-old without guardian approval).
So, to put it bluntly, as long as policy is adhered to with reasonable good faith, the Mass team is in charge during any given Liber XV celebration. The Priest and the Priestess are essentially acting with the authority of the Patricarch (in our current case, Frater Superior Hymenaeus Beta) and through his Primate in the U.S. (in our case, T. Apiryon, the Supreme and Holy King, Sabazius), who delegates his authority through his Bishops. During the celebration of the Mass, the Deacon and Children operate under the authority of the Priest and Priestess team. An ordained Deacon is actually oath-bound to assist in this way, who agrees to "abide by the policies of Ecclesia Gnostica Catholica, and that you will faithfully fulfill the functions of a Deacon, ever in service to your congregation, and under the direction of your Priest and Priestess."
With that said, a wise Mass team will take into consideration local traditions and social norms. However, that consideration does not take precedence over their own take on the ritual. This includes the actions of the People, who are, in essence, the sixth officer of Liber XV. It is the Deacon's job to instruct and lead the People in the particulars of the ceremony, as she is the conduit or viceroy representing the Mass team to the congregation.
To give an example, if I am doing Mass as Priest (and assuming the Priestess agrees with me), I want my Deacon to prep the People, because (1) I believe that this is a vital way that the Deacon can be "in service to [her] congregation," (2) I or the Priestess might have particular instruction to give that a non-officer will not be privy to, and (3) the Deacon is the connection between the Priest/ess and the People, and is therefore the natural officer to represent the Mass team thru instruction of the ritual particulars. While I might recognize that this is not traditionally how it is done at any given local body, I believe my reasons trump a tradition that does not have the Deacon give the pre-Mass rap, and that I have a right to have this happen when acting as Priest. Moreover, I believe the community should respect that right.
HOWEVER, this is as far as my insistence goes. As far as my example goes, Liber XV does not state anything about prepping the People beforehand. Therefore, I would NEVER insist that any other team MUST do what I do. The key element here is that--within the scope of policy, the literal script, and the sanctity of the body--the Mass team has full authority to decide how optional elements will be performed, assuming that they have been in communication with their supervising Bishops.
Tradition certainly has its pros and cons. It's fantastic when it provides a sense of continuity and community identity. Having a heritage can provide a group with a sense of pride and accomplishment, and should be celebrated. However, when it is used to stifle creativity and new ideas in a changing environment, it tends to lead to stagnation and a reduced ability to solve problems. Moreover, it can create a sense of exclusiveness, locking out new members from the cultural current.
I will continue to lobby for this general outlook for two main reasons: (1) I believe this is the way the Church is actually set up, and (2) it helps prevent stagnation and "right way" thinking while promoting tolerance of differences. In my experience, it also promotes critical thinking and an openness to trying out new ways to celebrate the ritual, because exploration is far more acceptable. As an example of this kind of benefit, various Priestesses have different personal stances on touching during communication, from heavy hugs, to hand holding, to hands off. In a culture where the community expects to be instructed in such areas, a priestess can be confident that her boundaries will be respected, especially if the Deacon is allowed to articulate her requirements to the congregation beforehand. Finally, another important benefit is that it places the responsibility of ritual quality squarely where it belongs: the Mass team.