I suspect I've spent as much time as any owner in and around the center channel area. The short answer is that there is no easy (or even hard) way to use the center tower for front storage (with the except of putting things in the existing cup holders). The number of modifications to the tower preclude an easy and aesthetic solution. The cubbie is the only storage in the front area that comes with the car and it's not closed.
For rear storage, there is an opportunity to craft something in the curved indentation in the back of the tower near the floor. It would leave the floor flat (to accommodate three rear passengers, but still be functional. I have a few ideas along those lines that I'll share once my current Model S project is completed and on the market.