Floppies were the most ubiquitous storage device for a while so it's no surprise. Nowadays it could be a few USB type A ports. We're slowly switching to USB type C but type A has now been standard for around two decades.
Damn, that phone prototype is crazy-small for the 1980s -- it looks like a Motorola Razr V3 (2004)!
Even if it were just a cordless landline phone (with less demanding hardware than a cellular phone), battery size would be a problem because lithium-ion hadn't been invented yet. I'm not sure Ni-Cd batteries that thin ever existed.