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, ...).

LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::string strAddress = request.params[0].get_str();
    CTxDestination dest = DecodeDestination(strAddress);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
    }
    auto keyid = GetKeyForDestination(*pwallet, dest);
    if (keyid.IsNull()) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to a key");
    }
    CKey vchSecret;
    if (!pwallet->GetKey(keyid, vchSecret)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Private key for address " + strAddress + " is not known");
    }
    return EncodeSecret(vchSecret);
}
UniValue dumpwallet(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 1)
        throw std::runtime_error(
            "dumpwallet \"filename\"\n"
            "\nDumps all wallet keys in a human-readable format to a server-side file. This does not allow overwriting existing files.\n"
            "Imported scripts are included in the dumpfile, but corresponding BIP173 addresses, etc. may not be added automatically by importwallet.\n"
            "Note that if your wallet contains keys which are not derived from your HD seed (e.g. imported keys), these are not covered by\n"