AA is not selling basic economy in many markets, and the upcharge from Blue Basic to Blue on longer flights can be quite a bit (e.g. $65). There was an interesting CrankyFlier article about their pricing strategy in April. Personally, I don't think AA will come out a winner because most people won't know that "no domestic BE" is a differentiator for AA.

Early boarding and priority security cost an airline nothing, regardless of if you're on a basic or standard fare. SDFC probably won't have that much uptake on B6 flights because they often don't have that many frequencies. Free checked bags do have an opportunity cost in case someone was going to pay for a checked bag, but are basically table stakes for reciprocal elite benefits.