Consider a traditional USD/EUR bank account. If your bank offers you a "vault" option to store your large balance to offer better reassurance that it won't get stolen from your "regular account"/wallet, aren't you going to have some serious concerns about security of the regular account? Instead of offering a "more secure account" why don't think just work on the fact that people feel that their regular accounts are insecure. This seems like a bandaid on the problem rather than the proper fix.
It's also overcomplicated. Now I have two account types and have to worry myself over what the differences are for accessing my money in each and how to use each. They're increasing the amount of friction it takes to get started rather than basing their model off a bank's model of "your account is as secure as it needs to be, just use one".