Bitcoin is a crypto currency. It's entire purpose is to be a secure, non-refundable, system of monetary exchange. If you want a payment processor that offers cancellations (PayPal for BTC), then that is what you will need to find, start, or contribute towards, but bitcoin isn't intended to be cancel-able, for a reason.
I don't think has asks for bitcoin transfers to be refundable, as the transfers wouln't hit the blockchain until the delay was over(as I understand it). this function may be usefull in some cases, but has imo no urgency. perhaps as a nice to have feature in bitcoind v4.x