I think that you could also look at the use of disguise and misrepresentation in the novel. The most obvious is Oliver, the "twist" who is mistaken for rags when he actually comes from riches. The Monk's perpetuate this mistaken identity in order to serve their own aims of claiming Oliver's inheritance for themselves. Nancy pretends to be Oliver's sister by putting on middle class clothes in order to get Oliver back to Fagin. Clothes as a means of identifying social class are important. Oliver is stripped of his clothes and pout into pauper clothes. If I were writing a thesis for a paper on this work, I would consider looking at the outward representations of class and status as displayed by clothes and manner of speaking, and the way that these "disguises" can and are used to meet individual desires.
Dickens, in fact, uses this theme as a means of satirizing class structure in Victorian England. You could even gop on to look at other class representations that are symbolized by dress, such as the way in which the Fagin boys almost worship handkerchiefs which they like to steal. These are symbols of affluence. If you carry a handkerchief, you are assumed to be a member of the upper class. If you wear the clothes of a workhouse person, you are seen as a pauper. Again, this is a way Dickens uses outside appearances as a means of denoting class differences from the perspective that people are viewed by society and judged by society by the clothes that they wear.