My bank charges 20DKK (~$3) for a SEPA transaction. I'd be really interested if you could show me a Danish bank that offers free SEPA transfers.
As for dispute resolution, I think it would be appropriate for this to be a third protocol layer -- on top of VISA-style clearing. I see no reason the clearing layer should handle this as well (and incorporating it into the Bitcoin layer would be true insanity, in my opinion). Nor do I see a reason it should be difficult. Costly, perhaps, but it's a simple matter of finding a mutually trusted third party, who won't release funds to the merchant until the consumer has received the goods.
The difficult bit of retail payments is not clearing but fraud and disputes, which bitcoin tends to wash its hands of.