I also feel that having a more lippy Oliver does not work. It makes you think there must be something to be said for the workhouse (not that we saw much of it) if it turns out such self-confident young men. It also means that there is not enough contrast between Oliver and the Dodger.
You may complain that it was also nonsense for Dickens to make Oliver emerge from the workhouse as a little gentleman, but that does seem to be what the story requires. The moral is that Dickens knows best.