Enoch (2005) argues that idealization is problematic for subjectivist theories:

The reading of the watch tracks the time—which is independent of it—only when all goes well, the perceptual impression tracks relative height—which is independent of this perception—only when all goes well. So there is reason to make sure—by idealizing—that all does go well. But had we taken the other Euthyphronic alternative regarding these matters things would have been very different. Had the time depended on the reading of my watch, had the reading of my watch made certain time-facts true, there would have been no reason (not this reason, anyway) to “idealize” my watch and see to it that the batteries are fully charged. In such a case, whatever the reading would be, that would be the right reading, because that this is the reading would make it right.

The natural rationale for idealization, the one exemplified by the time and relative-height examples, thus only applies to cases where the relevant procedure or response is thought of as tracking a truth inde-pendent of it. This does not necessarily rule out extensional equivalences between normative truths and our relevant responses. One may, for instance, hold a view that is an instance of “tracking internalism,”according to which, necessarily, one cannot have a (normative) reason without being motivated accordingly, not because motivations are part and parcel of (normative) reasons, but rather because our motivations necessarily track the independent truths about (normative) reasons. But typical idealizers do not think of their view in this way; they do not think of the relevant response as (necessarily) tracking an independent order of normative facts. As emphasized above, they think of the relevant response as constituting the relevant normative fact.

I'm not sure how relevant this objection is for CEV, though.