It should be possible to inject beans in implementations of javax.validation.ConstraintValidator.
E.g. MyFaces CODI supports it already for CDI (https://issues.apache.org/jira/browse/EXTCDI-20), however as mentioned in http://java.net/jira/browse/JAVASERVERFACES_SPEC_PUBLIC-763 a generic support would have to support JSR-330 (instead of JSR-299). The final approach has to be coordinated with all other JSRs which are going to provide such an injection support.
I'd definitely like to see some sort of DI support for constraint validators.
I'm not sure thought what we could do to achieve this from a Bean Validation point of view. Wouldn't that be the responsibility of the DI container? Spring already has support for this and for CDI there is besides CODI also Seam Validation. It might be a good idea to standardize that in the CDI spec.
Maybe you could provide some more information on the kind of support you have in mind?