Okay, so now we need a trust feature on both ends. After all, if you make a cash deposit, how are you going to be certain that the bitcoin seller is going to send you your coins? We are at a halfway trust position using Local Bitcoins as it is. There should be a way to go the other half of the trust using a bank account.
I'm not sure what you are saying here.
If you use localbitcoins, then localbitcoins holds the bitcoins so that the bitcoin seller can't run off with them. After you make the cash deposit, the seller should release the bitcoins to you. If they refuse to do so, then you can file a complaint with localbitcoins. As long as you can satisfactorily prove to localbitcoins that you made the deposit, they will release the bitcoins to you without the permission of the bitcoin seller.
If you don't trust localbitcoins, then you'll need to find someone else that both the buyer and the seller trust. If you are going to exchange fiat value (or much of anything else in the physical world) for bitcoins, then either one of you will need to trust the other, or you'll need to find an independent third party that you both trust.
The problem with reversible payment methods is that even if you find an independent third party that you both trust, the scammer can reverse the payment at a later time (after the bitcoins have been released). With PayPal and credit cards this can be months later. There aren't many people that are willing to wait for months after they've paid to receive their bitcoins from the independent third party. With personal checks and bank transfers, it is likely to be several weeks at least before the sender can no longer reverse the payment.