If you take the term dignity quite literally, following from its etymology, it is simply the sense of having value. So of course, the core of any ethics is going to dictate its own sense of dignity.
Since the word itself is simply about a 'sense' or an appearance, tou might perhaps, dispense with this extra wrapper if your ethics complete bounds itself in a way that avoids extending into aesthetics. I would suggest that systems that roll that sense of dignity produced by the ethics itself into the ethics proper cannot dispense with it. But more explicit forms of ethics that have less permeable boundaries around them, can.
Kantian ethics always presumes, in some sense that the primary value of autonomy comes 'pre-wrapped' with the assumption you are extending not only the right to self-determination, but that your rights are clear to you, and go unchallenged, whenever that is reasonable. On the other hand, this latter aspect is in some sense just about people being comfortable, which is 'officially' not an essential aspect of the system. Kant purposely avoids considering motivations that are simply about sentiments or humanity as valuable.
But at the same time, Kantian ethics passes over into all other fields of reasoning, including aesthetics. As humans from his culture, to have this polish stripped away would itself fail to be moral. If all of our decisions were contentious, and challenge was the order of the day, most of us would find that untenable. This is only because of our general sense of decorum, and not basic to morality, but it is still a moral maxim.
Utilitarianism generally also comes with a recognition that ugliness has negative value, and reaches over into a certain layer of aesthetic prescriptiveness. I cannot imagine a utilitarian motivation that would favor the kind of stress that having one's decisions constantly challenged. So I do not think Utilitarianism can do without a sense of dignity.
Even in the stripped-down, bare-metal, lassez-faire Capitalist economics that is the most oversimplified version of utilitarianism, there needs to be a sense that we all know the rules, for a market to function properly over time. Disobeying the basic principles of the system constitutes a form of cheating. And any concept of cheating comes with its own sense of dignity: When can one be accused of cheating? Is the accusation itself normalization or aggression? Are there compensations and punishments? Who decides them? Etc.
Even a Nietzschean ethics that recognizes the right of an individual to 'do art' on themselves would need a sense of dignity, if one that moves about as the individuals involved create different sorts of tension by refining power and power relations. The process of the ethics needs to remain possible, and without some breathing room around one's agenda, things would be too rigid.
But more self-consciously modern moralities have explicitly pointed out the damage done by decorum, in fixing social class boundaries, limiting individuals with unusual temperaments, affording different rights to the sexes, etc. without having to own up to the damage done. So something like social contract theory does not have permission to cross over and prescribe aesthetics.
If behavior is to be judged uniformly, based on principle or on shared taste, it is part of the contract, or it is not. Although the contract may be vague on the issue, the boundaries are those set by what we agreed to, whether or not that is clear yet. In that case, there is no need for an additional layer of 'dignity'.
