Opportunistic is the wrong word to use because
1) It is used already and has an existing meaning.
2) It short changes authenticated credential approaches such as DANE and PKIX.
Adept is a much more appropriate term to describe an approach that
essentially says
1) Determine the set of available keys by algorithm X.
2) Determine the set of keys that meet the security policy by algorithm Y.
3) The set of acceptable keys is the intersection of X and Y and the
preference within that intersection is determined by algorithm Z.