Sound to me like a big mistake. Wikisource is a source, not an editor ;
we have not to decide what is more valuable for the public. And soon or later there will be wars edit.
Why is it a "big mistake" to provide valuable, useful editions of classic works to the public under a free license?
Almost all "sources" require good editing, and any good library requires quality editions. If a good edition is not in the public domain, then just proofreading OCR won't produce a quality edition for your "free library".
Beyond that, there is no need to declare that Wikisource is THIS and not THAT. A more generous view of things will better serve both the project and the public.
And like I said, we've never had an edit war (in about 8 years). I tend to think that is because the people who edit texts and the process of editing texts are both less prone to edit wars than are Wikipedia articles. It is a different culture. Of course it could still happen, but then maybe it would be better not to have Wikipedia either since edit wars happen there?