This mode is actually supported by Silverfish already, it's just not exposed as an option users can change though the GUI yet, but it won't speed up play. The current setup will make it run slower and perform a lot worse than the bot does, because it's updating a lot more, waiting for the user to perform an action than it would when the bot was in control. You'll notice this as you try to play cards and stuff, since the client will be a lot more laggy (as you'll have to disable the bot's input control to interact with the client). A better alternative is to have it triggered on a button press rather than run automatically to avoid performance issues of trying to obtain and process so much information from the game so fast.
As mentioned in other threads, improvements to play speed is being worked on, but it's not a simple issue. There's a lot more going on in the client than users know about, but we'll get something worked out eventually.