If the devs can manage to get an agreement with some exchanges to put it on for non-variable amount then it couldn't change.
That won't work either, private exchanges (person to person, or alternative exchanges as well) can decrease the value of coin determined by supply and demand. Look at BTC now with the different USD/BTC exchanges. The value can sometimes be as much as 200 U.S. dollar from BTC-e and MtGox.
The value of the Euro, Dollar etc. is only what it is because they say it is and we believe it.
That's because we're forced to "believe" it due to legal tender laws. With Legal tender laws you have an unintended consequence called
Gresham's law takes effect. Basically bad money chases good money out of the system. As an example, try finding a 90% silver quarter in circulation now. People horde it because they know its worth far more than the quarter it represents in melt value. In theory this coin could run into the same problem due to the currency that will be used to supposedly back it's value. We all know that central banks only have a hammer and every thing is a nail. Meaning all they know how to do is inflate their currency for whatever possible problem comes along. Say this coin goes forward as is, the euro will continue to be inflated next to the dollar because the end of fiat currencies is inevitable. It's impossible to keep a system of debt going forever, you can't print a currency at interest and not print the interest to pay it. To me, that's the biggest flaw of this coin is backing it with a known inflating currency while limiting the supply of the coin. Is the dev, or someone going to continue watching the Forex looking for value deviations and adjust accordingly? Yeah a Euro is a Euro to the guys and gals out using them. But for Forex traders a Euro is worth a $1.35 one day, or $1.42 the next day. It's value does fluctuate just not as much as cryptos.
But if you think about it the value will change. The value of the coin changes on the price of the Euro and if you placed this against other coins on cryptcy I could see this working. That's the only way though, along with strong supporters.
Due to person to person transactions, or alternative exchanges I don't see how any exchange can keep the value of the coin to where the dev's of this coin would like them to be. Without the Dev's having 1,000,000,000 EUR to back each coin, or 100% premine they will never be able to keep the value of the coin for their intended target. The law of supply and demand mandate it. It would do the same to national currencies if central banks didn't inflate to make up for the rise and fall in interest rates.