You are right. I honestly believe, in fact, that nothing has a more unifying effect in a country than its currency. Everybody is constantly exchanging it and identifies with it. I kept most of the limited edition coins I came across for my children and nephews.
However, in order to produce a coin, you need to set an advance timeframe. If, in the context of the organization of the 150th anniversary celebrations, certain themes were chosen and you wanted to see them used at some point in this event, what would be the deadline to submit themes to you?