You could add api for sites like blockchain or inputs.io
Ew Inputs. That site is so insecure. The owners could steal your BTC any time they want, and you can't export your private keys.
Just don't use a web wallet for anything more than pocket change. For big stuff, use an encrypted desktop client or even an offline cold storage wallet on a Raspberry Pi.
Just like blockchain.info who could have been recording all your passwords that you feed to the API.
Not allowing people to export their private keys
is a good thing because private keys should not be exported or reused for security reasons.
You could have been recording our passwords for all we know. Your site could be a scam for all we know. Maybe you're just waiting until enough people store enough bitcoins to take the money and run? What's stopping you?