It's currently not possible to import (solvable) SegWit addresses (P2SH and native) using `importmulti`. I believe that's a shortcoming we should address before release.

My suggestion would be for P2WPKH (P2SH and native) to be supported without any extra arguments. This means that a P2WPKH address/script with corresponding private or public key should work. For P2SH it means checking if the supplied P2SH address perhaps matches the supplied public key or private key when converted to P2WPKH first.

To support P2WSH, I think we need an extra field "witnessScript". When supplied, it would either be required to match a P2WSH address/script directly, or if the address is P2SH, indirectly.
{
    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() != 0)
        throw std::runtime_error(
            "resendwallettransactions\n"
            "Immediately re-broadcast unconfirmed wallet transactions to all peers.\n"
            "Intended only for testing; the wallet code periodically re-broadcasts\n"
            "automatically.\n"
            "Returns an RPC error if -walletbroadcast is set to false.\n"
            "Returns array of transaction ids that were re-broadcast.\n"
            );
    if (!g_connman)
        throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
    LOCK2(cs_main, pwallet->cs_wallet);
    if (!pwallet->GetBroadcastTransactions()) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Error: Wallet transaction broadcasting is disabled with -walletbroadcast");
    }
    std::vector<uint256> txids = pwallet->ResendWalletTransactionsBefore(GetTime(), g_connman.get());
    UniValue result(UniValue::VARR);
    for (const uint256& txid : txids)
    {
        result.push_back(txid.ToString());
    }
    return result;
}
static UniValue listunspent(const JSONRPCRequest& request)