That’s the theory put forth today by Bernstein analyst Toni Sacconaghi, who believes Apple’s market-share aspirations for the iPhone are a lot like those for its iPod business. Sacconaghi sees an iPhone Nano or Mini as an inevitability, one that would dramatically expand Apple’s addressable market.

“We are surprised that Apple hasn’t moved sooner to introduce a lower priced offering that could help secure a more dominant installed base,” Sacconaghi said in a note to clients today. “After all, the smartphone world is a platform war, where first mover advantage and scale matters. The dual facts that (1) iPhone has not been available at several very important global carriers and that (2) it carries a very high price point have contributed to creating an opportunity for Android that has been successfully exploited. Particularly with Android now outselling iOS, the imperative for Apple to expand its installed base has never been higher.”

A scaled-down version of the iPhone with a cheaper data plan–or one that required no data plan at all–is one very obvious way of doing that. Roll out a device like that with a street price that falls somewhere between $149 and $199, says Sacconaghi, bring it those carriers that don’t yet offer the iPhone, and mass-market adoption will follow. Serious mass-market adoption.

“It is difficult to estimate the size of a market for a product that we don’t yet know the form-factor or timing for. But as a rough guide, we estimate that at an end-user price of $150-$200 and no data plan contract, Apple could address potentially all of the remaining smartphone segment, the non-smartphone postpaid segment, and about 15 percent of the non-smartphone prepaid segment. This would amount to an incremental 700M+ units and $90 billion in revenue in terms of market opportunity; even if Apple succeeded in capturing just 5 percent of these incremental units, it would add $12+ billion in revenues and $4.50+ in EPS.”