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.
"1. \"dummy\"    (string, optional) If set, should be \"*\" for backwards compatibility.\n"
            "2. count          (numeric, optional, default=10) The number of transactions to return\n"
            "3. skip           (numeric, optional, default=0) The number of transactions to skip\n"
            "4. include_watchonly (bool, optional, default=false) Include transactions to watch-only addresses (see 'importaddress')\n"
            "\nResult:\n"
            "[\n"
            "  {\n"
            "    \"address\":\"address\",    (string) The bitcoin address of the transaction.\n"
            "    \"category\":\"send|receive\", (string) The transaction category.\n"
            "    \"amount\": x.xxx,          (numeric) The amount in " + CURRENCY_UNIT + ". This is negative for the 'send' category, and is positive\n"
            "                                        for the 'receive' category,\n"
            "    \"label\": \"label\",       (string) A comment for the address/transaction, if any\n"
            "    \"vout\": n,                (numeric) the vout value\n"
            "    \"fee\": x.xxx,             (numeric) The amount of the fee in " + CURRENCY_UNIT + ". This is negative and only available for the \n"
            "                                         'send' category of transactions.\n"
            "    \"confirmations\": n,       (numeric) The number of confirmations for the transaction. Negative confirmations indicate the\n"
            "                                         transaction conflicts with the block chain\n"
            "    \"trusted\": xxx,           (bool) Whether we consider the outputs of this unconfirmed transaction safe to spend.\n"
            "    \"blockhash\": \"hashvalue\", (string) The block hash containing the transaction.\n"
            "    \"blockindex\": n,          (numeric) The index of the transaction in the block that includes it.\n"
            "    \"blocktime\": xxx,         (numeric) The block time in seconds since epoch (1 Jan 1970 GMT).\n"
            "    \"txid\": \"transactionid\", (string) The transaction id.\n"
            "    \"time\": xxx,              (numeric) The transaction time in seconds since epoch (midnight Jan 1 1970 GMT).\n"
            "    \"timereceived\": xxx,      (numeric) The time received in seconds since epoch (midnight Jan 1 1970 GMT).\n"
            "    \"comment\": \"...\",       (string) If a comment is associated with the transaction.\n"
            "    \"bip125-replaceable\": \"yes|no|unknown\",  (string) Whether this transaction could be replaced due to BIP125 (replace-by-fee);\n"
            "                                                     may be unknown for unconfirmed transactions not in the mempool\n"
            "    \"abandoned\": xxx          (bool) 'true' if the transaction has been abandoned (inputs are respendable). Only available for the \n"
            "                                         'send' category of transactions.\n"
            "  }\n"