I think if a good coder could make a multi-wallet for all alt-coins including BTC safe, they could add in an internal exchange system that would probably render most exchanges obsolete. Not to mention the potential chance to improve transaction speeds am I right? (if not improve at least be more secure in the sense of not needing web hosting) not a coder myself but this idea did turn up in my head so I googled it.
Each hot wallet requires the entire blockchain being run on your machine. It is not technically feasible for an average person to run that many wallets.