The Euro Landscape Is Changing

I think the author of the article lacks some understanding about Euro coins.

Only coins from 1 cent to 2 euro are bound to have common and national side and must follow guidelines.

Any country can issue Commemorative coins in any denomination (1,5€, 3€, 5€, 7,5€ are some examples) and from any material (gold, silver, copper, fancy new materials ...). However those coins are only legal tender in the issuing country.
The practice is far from new; it goes back to introduction of Euro in 2002. There's no country in Eurozone that has not, to my knowledge, issued at least one such a coin. A quick glance at any good (or even bad for that matter) catalogue will tell you the same thing.

Sorry, but it's hard to take seriously writing from someone who did not do his research.