The remote named PM wishes to delegate most of his powers to two representatives on site. One being a person undertaking the Supervisor role and the other acting, for want of a better term, as say assistant PM.
Of course there is no such role of assistant PM under the contract but that person requires delegated powers hence the question.
There are no real restrictions here as to what or to who they delegate their powers down to. Obviously they will act on their behalf so they should be confident that they are experienced and capable enough to act on the PM’s behalf. Just very important that this delegation is communicated in writing (13.1) and separately from any other communication (13.7).
The fact some powers are being delegated to the Supervisor is not a contractual issue (although that person may have some internal issues when they are making a decision with their different PM or Supervisor hat on).