Some comments from @sipa in #12702.

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Yes, I think `importmulti` is superior in every way, except:
* Slightly less convenient to use (it requires redundant information, as you have to explicitly state what you want to import, and then give the keys/... to enable that).
* ~Doesn't support P2SH-P2WPKH yet~. Added in #14454

The latter can be fixed by just adding support for that case. The former can be improved by adding 'default' cases (e.g. if you prove a WIF private key, it can permit omitting the address, ...).

bool operator()(const CKeyID &keyID) {
        if (pwallet) {
            CScript basescript = GetScriptForDestination(keyID);
            CScript witscript = GetScriptForWitness(basescript);
            if (!IsSolvable(*pwallet, witscript)) {
                return false;
            }
            return ExtractDestination(witscript, result);
        }
        return false;
    }
    bool operator()(const CScriptID &scriptID) {
        CScript subscript;
        if (pwallet && pwallet->GetCScript(scriptID, subscript)) {
            int witnessversion;
            std::vector<unsigned char> witprog;
            if (subscript.IsWitnessProgram(witnessversion, witprog)) {
                ExtractDestination(subscript, result);
                already_witness = true;
                return true;
            }
            CScript witscript = GetScriptForWitness(subscript);
            if (!IsSolvable(*pwallet, witscript)) {
                return false;
            }
            return ExtractDestination(witscript, result);
        }
        return false;
    }
    bool operator()(const WitnessV0KeyHash& id)