Is it permissible for the two witnesses to the marriage contract to bear witness if the guardian is absent and his consent is in writing, and is it permissible for the absent guardian to authorize any sane Muslim person without specifying a particular individual?

If the guardian deputizes someone to perform the marriage contract on behalf of an absent party, then the contract and the testimony thereon are valid. However, if the guardian does not deputize anyone, and the woman marries herself or is married by someone who has no guardianship, then the contract is invalid according to the majority of scholars, and testimony thereon is not permissible. As for the guardian deputizing someone to perform the marriage contract without specifying the individual, this is not valid, and specifying the agent is a condition for the validity of the deputization.