I think before to start, you will need to develope more your idea, how an user could claim their cold storage, how you can prove that you won't run with the money.
This is not something that someone can prove. In order for this to be a remotely viable option, the OP will need to demonstrate his integrity over time, including his ability to safeguard other people's money over time.
I think a better solution would probably be something along the lines of how the coinbase vault works. The OP would only control 1 of 3 keys, and would only sign transactions after a certain, agreed upon time delay.