maybe
needs some authorization vs WebSockets' flood from bag guys (direction: from client to server)

something like this:
- some cookie received from Trade API for websocket connection to MtGox. this cookie valid only next hour (5-10-30min)
- on new connection to websocket client must send this cookie to server. if cookie is valid automatic subscribing will do..
cons: more difficult process for connection

or:
- using SSL/TLS encrypted WebSocekts.
pro: can refuse polling Trade API and do all orders and receive statuses over WS
cons: need implementations for different languages

imho
It will be good to send 10-30 best Sell and Buy depths one new connection after subsribe to depth channel : price, type, ABSOLUTE-volume
After that depth data sent in relative manner: +volume, -volume
It gives knowledge to robots(or men) of current volumes for asks & bids.

technically:
JSON changes to this: add new attr to "depth": "abs"=X: where X = "1" for absolute volume; "0" or absent attr - relative volume as now
That data can be cashed on server for all new clients. Depth changes updates cache. Need to generate JSON (for sent) on request only - more expansive operation than just update some structs in cache.

PS
Sorry for my Russian English

I wrote some code in C# for MonoDevelop or Visual Studio
MtGox & IMtGoxHandler & TestMtGox - for making orders
  FetchCash
  FetchOrders
  Place/CancelBuyOrder
  Place/CancelSellOrder
  .Handler - interface for responses & errors
WebSocket & Program - for read trades events
  .OnData - delegate received string (in JSON format) for any channel

https://rapidshare.com/files/3646016978/MtGoxApp.zip