I wouldn't give up on using remoting. Performance of remoting will be much better than JSON. Remember ActionScript doesn't have a method to decode JSON, so you'd need to use an AS library which will be slower than anything built into the player. You'd be better of using XML than JSON.
You should be able to exclude specific properties as desired by marking them as transient. ActionScript has [Transient] metadata and the idea came from Java. The C# library we use for remoting has Transient support. I'm sure BlazeDS does too.
Debugging is easy with the right tools. You should get Charles. It provides very nice views of AMF request and response messages (assuming you're using HTTP and not RTMP, I don't know about RTMP debugging).
You also seem to be choosing between BlazeDS and anything-not-remoting. You have more options. BlazeDS is just one remoting implementation that Adobe made available. They also have a commercial one. There are also many open-source remoting projects available. We use a wonderful one for C# called Fluorine. Open-source Java options are Red5 and OpenAMF, but I think there are others as well.
There's also a distinction between RTMP and HTTP remoting. You can get data into Flex through either of these protocols and each will have it's advantages/disadvantages. I personally prefer HTTP remoting unless you absolutely need the functionality RTMP provides (push, streaming). HTTP will be easier to debug and should not have problems with a load balancer--it's just HTTP calls where the content happens to be binary.