Verifying a MetaTransaction, how to deal with variable structs?

Smart Contracts
1

Suppose we have a verifying contract that relays to arbitrary contracts. The appropriate signature and parameter types of the given contract method is known before signing.

The signing method being used is eth_signTypedData_v3 via MetaMask.

Would you be able to send the method signature along with its parameter data for verification?

I ask because I see most signatures hardcoded in verifying contracts and want to make sure this isn't a security vulnerability. Below is the meat of what I'm talking about

//Client
 const msgParams = JSON.stringify({types:
        {
        EIP712Domain:[
          {name:"name",type:"string"},
          {name:"version",type:"string"},
          {name:"chainId",type:"uint256"},
          {name:"verifyingContract",type:"address"}
        ],
        Outlet:[
          {name:"signature",type:"string"}
          {name:"sender",type:"address"},
          {name:"_nonce",type:"uint256"},
          {name:"deadline", type:"uint256"}
        ]
      },
      //make sure to replace verifyingContract with address of deployed contract
      primaryType:"Outlet",
      domain:{name:"SetTest",version:"1",chainId:342,verifyingContract:0x482959AIFIJF...},
      message:{
        signature:"play(address sender, uint256 _nonce, uint256 deadline, uint8 choice)",
        sender: 0x252AD....,
        _nonce: 31,
        deadline: Date.now() + 10000;
      }
      })

Then on the verifying contract (hashStruct part).

function executeSetIfSignatureMatch(

    uint8 v,
    bytes32 r,
    bytes32 s,
    string signature,
    address sender,
    uint256 _nonce,
    uint256 deadline
  ) external {
    require(block.timestamp < deadline, "Signed transaction expired");
    uint256 chainId = 342;
    bytes32 eip712DomainHash = keccak256(
        abi.encode(
            keccak256(
                "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
            ),
            keccak256(bytes("SetTest")),
            keccak256(bytes("1")),
            chainId,
            address(this)
        )
    );  

    bytes32 hashStruct = keccak256(
      abi.encode(
          keccak256(signature),
          sender,
          _nonce,
          deadline

        )

    );
    bytes32 hash = keccak256(abi.encodePacked("\x19\x01", eip712DomainHash, hashStruct));
    address signer = ecrecover(hash, v, r, s);
    require(signer == sender, "MyFunction: invalid signature");
    require(signer != address(0), "ECDSA: invalid signature");