addmultisigaddress creates an address respecting the setting, being unable to generate a specific type of address without also adding it to the wallet seems wrong.

I suppose in the future `addresstype` may be refactored to be wallet-specific, which would leave this non-wallet rpc call without an argument. Perhaps there should just be an optional parameter to set it.
{
        already_witness = true;
        result = id;
        return true;
    }
    bool operator()(const WitnessV0ScriptHash& id)
    {
        already_witness = true;
        result = id;
        return true;
    }
    template<typename T>
    bool operator()(const T& dest) { return false; }
};
static UniValue addwitnessaddress(const JSONRPCRequest& request)