Great initiative!
wonder if we could also use a scheme like @bitgamma was once proposing in another context (Non-wallet usage of keys derived from BIP-32 trees) - so we would use different BIP-32 paths for each dApp.
This would have the advantage that we could directly use it with existing hardware wallets. In the above scheme hardware wallets would need to implement a new function to be compatible. The disadvantage would be that the chance of collisions between dapps is higher. But it would still be better than the status quo.