Henry Sidgwick in "The Methods of Ethics" actually makes the argument that Utilitarianism can be thought of as having a single predominant rule, namely the Greatest Happiness Principle, and that all other correct moral rules could follow from it, if you just looked closely enough at what a given rule was really saying. He noted that when properly expanded, a moral rule is essentially an injunction to act a certain way in a particular circumstance, that is universal to any person in identical circumstances. He also had some interesting things to say about the relationships between virtues and Utilitarianism, and more or less tried to show that the various commonly valued virtues could be inferred from a Utilitarian perspective.
Of course Sidgwick was arguing in a time before the clear-cut delineation of moral systems into "Deontological", "Consequentialist", and "Virtue Ethics". But I thought it would be useful to point out that early classical Utilitarian thinkers did not see these clear-cut delineations and instead, often made use of the language of rules and virtues to further their case for Utilitarianism as a comprehensive and inclusive moral theory.
I have previously been saying things like "consequentialism is obviously correct". But it occurred to me that this was gibberish this morning.
I maintain that, for any consequentialist goal, you can construct a set of deontological rules which will achieve approximately the same outcome. The more fidelity you require, the more rules you'll have to make (so of course it's only isomorphic in the limit).
Similarly, for any given deontological system, one can construct a set of virtues which will cause the same behavior (e.g., "don't murder" becomes "it is virtuous to be the sort of person who doesn't murder")
The opposite is also true. Given a virtue ethics system, one can construct deontological rules which will cause the same things to happen. And given deontological rules, it's easy to get a consequentialist system by predicting what the rules will cause to happen and then calling that your desired outcome.
Given that you can phrase your desired (outcome, virtues, rules) in any system, it's really silly to argue about which system is the "correct" one.
Instead, recognize that some ethical systems are better for some tasks. Want to compute actions given limited computation? Better use deontological rules or maybe virtue ethics. Want to plan a society that makes everyone "happy" for some value of "happy"? Better use consequentialist reasoning.
Last thought: none of the three frameworks actually gives any insight into morality. Deontology leaves the question of "what rules?", virtue ethics leaves the question of "what virtues?", and consequentialism leaves the question of "what outcome?". The hard part of ethics is answering those questions.
(ducks before accusations of misusing "isomorphic")