For several years now, the IESG and IAB have given their liaisons careful instructions. Each year, those instructions are reviewed with feedback from the previous year liaison. In my opinion, this is the right place for the annual review of the instructions. However, I do think that there can be a bit more guidance in BCP 10 that applies to all of the liaisons. I have a few thoughts:
1. The liaison is expected to act in the best interest of the IETF.
2. During NomCom calls and meetings, the liaison is expected to represent the views of the leadership body rather than personal opinion.
3. The liaison may provide personal feedback to NomCom, but they should only do so using communication channels available to all IETF participants.
To me, these are consistent with the language that is already present in RFC 3777:
Liaisons are expected to represent the views of their respective
organizations during the deliberations of the committee. They
should provide information as requested or when they believe it
would be helpful to the committee.
Russ