It is an interesting idea. A lot of "Traditional" bank accounts (at least in Australia) have tiered interest rates. eg: First $x, 4%, anything over $X, 0.5% (probably because they don't want the liability of paying massive interest every month) - just means people who are parking their large sums of capital in accounts spread them out across multiple accounts.
How would hive power delegations impact the interest. Would it need to be natively held HP?