Assuming the light green of the first map represents ethnic Farsis, it looks like Iran is a fairly solid Farsi core (the gap in the middle of the Farsi ring being, I believe, harsh desert hardly inhabited by anyone) with peripheral conquests; the most "balkanizable" region being the northwest, but with pieces more or less ready to snip off on the northeast and southeast too. But that done, the Farsi core remains, unless it is subdivided on sectarian lines.
Which I think unlikely but not impossible; modern Iran can be defined as beginning when a Shah in I believe the 17th century adopted a particular Shi'ite sect as the state religion and imposed it--Farsi Sunnis would have converted or been eliminated but I know rival Shi'ite sects have indeed survived in Iranian territory--while I doubt these divide the Farsi, and assume they are held to by people already ethnically separate from the Farsi, I could be wrong about that.
If the Farsi don't come pre-subdivided, a colonial era partition between the Russians and British could sunder the northern Farsi from the southern, then post-1917, if the Bolsheviks manage to hang on to the northern Farsi province and eventually create a Persian SSR, it would of course by 1990 be culturally very different from the British-dominated part, which might or might not have gone its separate way from the Empire by then (almost certainly, it would hardly be the last bit of Empire! Nor stay in the Commonwealth given a choice, probably) but would surely not let itself get belatedly taken by the Soviets either. So assuming that both British and Soviet empires go the way of the dodo, the splitting of the Farsi nation would still be an accomplished fact and reunion would be problematic.
But all this said, I have to say I find the project rather sad; my impression is that Iran is one of the more impressive examples of successful state-building, with its peripheral minority ethnicities rather more smoothly reconciled to their membership in the larger nation than is generally the case; breaking it up seems a shame.
And the upshot is not so much a broken mosaic as several such lying around a monolithic, or perhaps broken in two, Farsi center that historically subjugated the other pieces centuries ago and might well re-incorporate them once whatever political storm that broke their hold on them has come and gone.