My first thought is the 16GB be upgraded with a 2.5" hard drive like the 'Pro' model uses?
The console has no visible screws; the bottom readily popped off with a plastic tool.
Below are images of the innards of the nVidia Shield Android TV (note: serials obfuscated).
Initial opening; note the 2.5" filler in middle
HD filler and cabling removed. No obvious SATA ports.
Also to note is a metal shield that was covering some memory (?) chips below the CPU:
The metal shield was held in place by the tape holding the cables... (odd)
Interesting cable; the J1 end looks like a BGA.
Section of board where J1 connects; additional unused connector is located above.
Two metal pegs align and the screw secures the the contacts.
Console partially re-assembled with base
Thoughts: no obvious SATA or power connectors on board. There is a possibility that a second cable may be used in the pro version that would connect the additional space above J1 to a SATA cable? Or is the the 16GB flash on a board that can readily be removed and and replaced with a board that supports SATA?
The nVidia Shield Pro Android TV isn't due to be released for another few weeks; hopefully more info will be forthcoming once it has been released.