Say what?
Dispute - How is this any different than today. The credit card company is the arbitrator. Also, will this new arbitrator process in bitcoin-land cost me less than in credit-card land? Also, where is the improvement on the status-quo in this new scenario??
Secure - I concede that what you say sounds possible. Perhaps with a nice UX, but I don't see anything like you suggested available today. Also, how much will this online service cost? Will it be cheaper than government-backed money (ie. Chase/Bank-of-America/Credit Union/etc).
Again, all the solutions I see to have bitcoin lead to mass adoption are solutions that seem to add costs that will lead it to be no better than using current infrastructure.
Regarding disputes, the difference is that the arbitrator isn't involved at all if there's no dispute. He's not taking a piece of every transaction whether there's a dispute or not.
To dispute a charge afterwards, require up front that the merchant issue a refund transaction, which goes through if it's signed by any two of (buyer, seller, arbitrator). The arbitrator will charge a fee for this, but only has to get involved if buyer and seller dispute.
To secure coins, make transactions which pull them out of a storage address, which must be signed by any two of (the key on your computer/phone, a key held by an online service provider, a paper key in your safe deposit). The online service can't steal your money, someone who gets your phone can't steal it without your password to the online service, and if the online service disappears you use the paper key to get the money.
Aside from paper key storage, all this can be automated and transparent in everyday operation.