One thing that I have reservations with is the security of your private keys. Though the dev stated on how to handle such situation, still, I'm not yet convinced regarding security concerns. Is there a server that will serve as data storage of your clients?
It's a very understandable concern, that's why we put a lot of effort and development time into creating an air-tight environment where the servers are completely isolated from the internet and the data is encrypted both at rest and when sent.
Communication is done directly with the exchange via HTTPS, thus avoiding man in the middle attacks.
In addition the user can opt in to only unlock and decrypt when they enter the 2 Factor Authentication code.
We hope this answers your concerns.