We do not want to store the private keys of the wallet, we want this to be done by a reputable third party. For example we would like to create a blockchain.info wallet for email [email protected] without us storing anything sensitive about this wallet. Basically all we need is to get back from API the wallet address just created for user: [email protected]. And then, [email protected] could go to blockchain.info (or any other provider) and use the wallet directly on their website or through their mobile apps.
Your comments and suggestions are more than welcome.