According to Wikipedia, Namecoin uses proof-of-work just like Bitcoin, and is therefore very energy-intensive / an environmental disaster. Therefore I could not support Namecoin even if it works perfectly as you say it does. We're going to need a more environmentally-friendly solution to decentralizing DNS.
As long as Bitcoin exists you can do merged mining with Namecoin. This means there is literally zero additional cost and impact on the environment for mining.
If the very unlikely case occurs and bitcoin stops being a thing there is always the possibility to change the POW algorithm. Until then Namecoin is a solution that works ultra reliably since years and most importantly unlike other solutions it works today.
If Namecoin were to become popular, wouldn't that encourage more mining of Bitcoin even if you were doing merged mining? It seems like if Namecoin took off then people would just say the reverse, "Don't worry about the environmental damage of Bitcoin, people were already mining Namecoin so there's no additional harm."
Do you assume that if Namecoin were to become super popular, the price of its coin would become very high? I don't see why. Can you explain this assumption?
Namecoins are not Bitcoins, they're not supposed to be used as a currency, so the logic that the popularity of Namecoin would create a huge raise in its price is not straightforward.
It will take a long time until NMC will be as popular as BTC if ever. Until then let other people figure out how to implement a proper proof of stake and switch to it when the time comes.
In the mean time merged mining is the best compromise between rock solid chain security and environmental impact.
