Take a look at actual online wallets, such as blockchain.info for instance. Is that possible to create the same type of online website but that allows cold storage wallets creation ?
didn't really understand what do you mean but from what i understood yes you can create a cold storage wallets and put it in an online service just like coinbase, xapo and blockchain.info if i am not wrong...etc
theses services offers a hot and a cold wallets called vault
if you mean creating by your own a service offering only a cold storage then i would ask what is the point? i can put my money in my secured pc or hardware and be much safer
EDIT: vault*