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.
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.
Securing Bitcoin is a solved problem. Trezor is bullet proof piece of open hardware already working with multiple software backends, including two android wallets. And it's easy to use, as simple or even simpler than online banking. And it's not the only one - there are other hardware wallets. For corporations today there is multi-sig and an improvement over multi-sig, called treshold signatures, currently in development.
Trezor has solved Bitcoin's security problems in the same way that PGP has solved internet messaging security; that is, amazing technology exists that addresses real problems, but in practice the problems are still prominent. Security is a major problem for the internet, and a much bigger problem for bitcoin since the incumbent system provides nearly identical services with a substantially smaller risk of losing real money.
1) Chargebacks, there is a way to dispute a charge after-the-fact, without the merchant's approval.
2) Stolen plastic means I don't lose my money.
These two things (probably others) are reasons I have trouble believing bitcoin is the new thing we'll all use eventually. Never mind that I can't see anyone I know using it. Good luck securing coins (they would never be able to do it themselves, and third-party services usually need some kind of private key. How is this better than a normal bank account??)
Also, it's not exactly easy to get. Sure, there are sites that verify your identity and allow you to buy with credit card, but then, why use the middle-man? I can buy what I want directly with credit card. I have yet to try a bitcoin ATM, this may work.