Habits induces correlations between choices in similar epistemic circumstances. A person who has behaved courageously in the face of physical danger on ten past occasions is more likely to be a physically courageous person, and therefore is more likely to behave courageously now when again facing physical danger, even when we control for the considerations on the basis of which we are deciding, unlike a fair coin which is not more likely to land hands just because on the ten past occasions it has done so. Our choices, moreover, modify our habits thereby even further increasing these correlations.
Now imagine persons that do not have habits in this sense. They make their choices based on the considerations present in each case, on a case by case basis. The fact that they have braved physical danger ten times does not make it more likely that they will brave it now, as long as one controls for the considerations present in the cases. Moreover, I will suppose that the motivational strength of the considerations they are deciding on the basis of does not change over time. They always find duty to have a certain pull and they always find convenience to have a certain pull, and the degree of pull does not change.
Such persons would not have character in the way we understand character. They would have neither virtues nor vices. They would have much less control over the shape of their lives. For we can shape our futures by inducing in ourselves a certain character. They could, however, influence the shape of their lives through rational means, by gaining new beliefs or by creating reasons to act.
It would be difficult for such beings to live in community. But we could imagine that one of their very clever engineers builds a mechanical sovereign who enforces basic rules for harmonious living through harsh punishment. For although there are no correlations between choices made in similar circumstances, one could change the circumstances to increase the weight of considerations in favor of actions that conduce to harmonious living. Or a prophet could convince the people that great rewards for virtue and harsh punishments for vice follow in an afterlife, and that, too, would conduce to harmony. But that still wouldn't be virtue.
The lives of such beings would be less storied. They would not exhibit the good of making a certain kind of person out of oneself. There are, indeed, many goods that they would lack.
But without any virtues or vices, these beings could still could have morally significant freedom. They could freely choose, on a case-by-case basis, whether to follow duty or some other consideration. Many of the familiar moral norms that bind us could apply to them. It would be no more permissible for them to kill the innocent or build palaces on the backs of the suffering poor than it is for us. They would have one fewer reason in favor of doing the right thing, though. If I build a palace on the backs of the suffering poor, I become a more vicious person. That wouldn't happen to them. But they would still have the simple reason that it's wrong to do this, together with extrinsic considerations coming from hope of reward or fear of punishment. And that I will become a more vicious person is only an extrinsic consideration against committing an action, anyway.
Virtue ethicists will probably disagree with me that such beings couldn't have morality. So much worse for virtue ethics. Virtues are an important component of human moral life, but I think they are not a component of moral life in general as such, just as physical interaction is an important component of human moral life, but isn't a component of moral life in general (angels have a moral life but as far as we know they have no physical interaction).