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, ...).

if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 2) {
        throw std::runtime_error(
            "walletpassphrase \"passphrase\" timeout\n"
            "\nStores the wallet decryption key in memory for 'timeout' seconds.\n"
            "This is needed prior to performing transactions related to private keys such as sending bitcoins\n"
            "\nArguments:\n"
            "1. \"passphrase\"     (string, required) The wallet passphrase\n"
            "2. timeout            (numeric, required) The time to keep the decryption key in seconds; capped at 100000000 (~3 years).\n"
            "\nNote:\n"
            "Issuing the walletpassphrase command while the wallet is already unlocked will set a new unlock\n"
            "time that overrides the old one.\n"
            "\nExamples:\n"
            "\nUnlock the wallet for 60 seconds\n"
            + HelpExampleCli("walletpassphrase", "\"my pass phrase\" 60") +
            "\nLock the wallet again (before 60 seconds)\n"
            + HelpExampleCli("walletlock", "") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("walletpassphrase", "\"my pass phrase\", 60")
        );
    }
    LOCK2(cs_main, pwallet->cs_wallet);
    if (!pwallet->IsCrypted()) {
        throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletpassphrase was called.");
    }
    
    SecureString strWalletPass;
    strWalletPass.reserve(100);