I think this would devalue bitcoins, as well as any other coins that get added.  Hundreds of new coins will be added at no extra cost (as markm already confirmed).  All of those coins will be at jeopardy of losing value and might even get rejected.

This would be akin to everyone being able to print their own money and trying to get others to accept it.  With a few select currencies, it's easy for them to succeed.  With thousands to choose from, people aren't going to accept every type of payment someone thinks up.

As good as it might sound, especially for miners, this will probably lead to demise of many currencies, many of which probably didn't have a chance anyway but some that might have had a chance will die off as well.

Isn't the allure of BTC and other currencies like NMC the idea that an entity isn't able to print money whenever they feel like it?  This would be the same thing.  Miners would be mining mainly for BTC while in the process, printing extra money that will end up having a nearly constant exchange rate between BTC, NMC, etc, thus increasing the money supply and devaluing all of those currencies.  People are worried about the US having to print money to stay afloat because it could eventually lead to hyperinflation making the USD worthless.  All the coins following this path will also have that same risk.  People want to adopt BTC because they believe that can't happen with the currency.

For all of our sake, I hope everyone will reject this idea and it won't make it into any official branch, or even unofficial ones.