No, we're not going to repair invalid ids automatically, and Sigil is no longer in the epub validation game
itself. Validation is done by plugins. If you consider Epubcheck's error message to be unhelpful, you should consider reporting this to the
Epubcheck developers.
Sigil's validation plugin framework offers plugin developers a way to create their own error-checking routines that go above and beyond what EpubCheck looks for (or how it describes a problem). Perhaps you can convince one to compile a list of extra checks/warnings into plugin that might be more helpful to neophytes.