Some comments from @sipa in #12702.

___

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, ...).

std::vector<CPubKey> pubkeys;
    for (unsigned int i = 0; i < keys_or_addrs.size(); ++i) {
        if (IsHex(keys_or_addrs[i].get_str()) && (keys_or_addrs[i].get_str().length() == 66 || keys_or_addrs[i].get_str().length() == 130)) {
            pubkeys.push_back(HexToPubKey(keys_or_addrs[i].get_str()));
        } else {
            pubkeys.push_back(AddrToPubKey(pwallet, keys_or_addrs[i].get_str()));
        }
    }
    OutputType output_type = pwallet->m_default_address_type;
    if (!request.params[3].isNull()) {
        if (!ParseOutputType(request.params[3].get_str(), output_type)) {
            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Unknown address type '%s'", request.params[3].get_str()));
        }
    }
    
    CScript inner = CreateMultisigRedeemscript(required, pubkeys);
    CTxDestination dest = AddAndGetDestinationForScript(*pwallet, inner, output_type);
    pwallet->SetAddressBook(dest, label, "send");
    UniValue result(UniValue::VOBJ);
    result.pushKV("address", EncodeDestination(dest));
    result.pushKV("redeemScript", HexStr(inner.begin(), inner.end()));
    return result;
}
class Witnessifier : public boost::static_visitor<bool>
{
public:
    CWallet * const pwallet;
    CTxDestination result;
    bool already_witness;
    explicit Witnessifier(CWallet *_pwallet) : pwallet(_pwallet), already_witness(false) {}