Exactly why waste 1/2 hr arguing with the bank for something that may not be possible when you can find a solution yourself within a few minutes. Having a secondary account also helps you keep your expenses under a limit/budget. Nevertheless, I don't know why people keep worrying about it specially since you're never responsible for any unauthorized charges. And nowadays most banks have some sort of security measures in place that allows them to monitor and flag suspicious or unusual activity. Add to that, you have Visa/MC's own network security which alerts member banks so it's very unlikely a fraudster will be able to get away with 10K in unauthorized purchases without even triggering some kind of hold or alert from the bank. Finally, you do that it's possible to skim an ATM-only card and capture its PIN? So having an ATM card doesn't necessarily give you any more protection than a debit card.

That being said, I do know that BOA allows you to set your own purchase limits on their debit card by yourself online. However, they charge foreign transaction fees unlike Schwab/Fidelity. In addition, HSBC issues an only ATM card but they also charge forex fees.