I like Eevee... and having another Pokemon that is like Eevee, kinda takes away from what makes Eevee... well... Eevee.
I wouldn't worry about that unless it had 5 or more evolutions. The fact that the hypothetical Eevee Gen VI equivalent would be a knockoff would take away from its own uniqueness. People still like Hitmonlee and Hitmonchan, but no one gives a flying crap about Sawk and Throh. It's hard to care about a Pokémon that is a blatant retread.
I'm not saying a Pokémon using a similar concept couldn't work, but they'd need to distinguish it enough so that it is no longer equivalent to Eevee.
2/10 topic by the way.
Why do I have to move with the crowd of kids that hardly notice I'm around? I work myself to death just to fit in.