Iranian Plateau seems too suited for the rise of an unified state, no?
Perhaps Medians last longer and after that, another people rise up?
Is it too late for an Elamite revival?
It was really great opportunity to create large empire so someone else, perhaps Medians, would take place of Persians or there would be some another Indo-Iranian group creating empire.
It is often the case that people on this forum have miscellaneous or frivolous questions that could be easily answered by the many experts on this forum but are difficult to find the answer to on Google Scholar/Books or Wikipedia because they don't often deal in alternatives. There are other...