Think of it like an intermediate step for the 99% of the world that doesn't "get" BTC yet. A "dollar" cryptocurrency would be easier for them to understand. Once they had more familiarity and comfort with cryptocurrencies, they would hopefully be interested in acquiring BTC.
The main problem most ppl I talk to have with Bitcoin is that you cant buy "anything normal" with it. The great thing about USD or EUR or AUD or whatever is that "everyone" uses it.
Why is that? Well its because the state makes it a form of exchange that has be accepted. Noone does this for BTC. BTC only has value because all of us using it agree that is has.
Fiat money has value because a state says it has a value and people agree that this state is trustworthy to a certain degree.
So your solution to tie a cryptocurrency to fiatmoney is not helping at all, what helps BTC the most is more ways to spend it, more shops to accept it, more services to get with it. The more you can do with BTC the higher its value.