If Iran was serious, then they would use Ethereum or Bitcoin. They would make an exchange in their country to get local currency in/out Ethereum. The exchange could allow local banks to transfer in/out (ACH-like) to the exchange to get in/out between Ethereum and their local currency. Then all cross-border controls are gone by Ethereum senders and receivers crossing borders.

The only reason not to is:

1) They don't want local currency holders expropriating their capital

2) It could result in their local currency having high inflation or even possible collapse down the road

But... if cross-border flow was really their goal, then they would use Ethereum.