Mouse, keyboard and a screen would already cover the needs for most users. No need to wait until everything just works. As for the ecosystem, Apple’s Neo is a phone connected to a bunch of peripherals. Even on limited iPhone/iPad OS a more desktop like interface could easily be implemented. The iPad already has some half decent desktop approximation.

The hard part is getting Apple to cannibalize their desktop and tablet related sales. Because they’re the only ones with all the tools in the box. Samsung doesn’t have any proper OS of their own to take this role, they bolt it on Android.