Override type read/write functions per field/parameter

Example.cs

    public class PackedIntSerializer : IMirrorSerializer<int>
    {
        public int Read(NetworkReader reader)
        {
            // unpack
        }

        public void Write(NetworkWriter writer, int value)
        {
            // pack
        }
    }

    public class MyBehaviour : NetworkBehaviour
    {
        [SyncVar(serializer = typeof(PackedIntSerializer))]
        public int MyValue;


        [ClientRpc]
        public void RpcDoStuff([NetworkSerializer(serializer = typeof(PackedIntSerializer))] int count)
        {

        }
    }

    public struct MyMessage : NetworkMessage
    {
        [NetworkSerializer(serializer = typeof(PackedIntSerializer))]
        public int MyValue;
    }

IMirrorSerializer.cs

    public interface IMirrorSerializer<T>
    {
        void Write(NetworkWriter writer, T value);
        T Read(NetworkReader reader);
    }