I'm not sure I understand the question, but I deal with several studios that "mix by mail" - Clients will send in "home brewed" tracks, along with a representative mix of what they're shooting for as far as levels are concerned and they'll (the studios) will attempt to make a more polished and refined set of mixes for them.
Two places that come to mind -
www.farviewrecording.com and
www.bluebearsound.com
After that, they may or may not send it off to a mastering facility for a final "detailing" job and assembly of the production master.
One place that comes to mind - Well, I won't go there.
But in short, it all depends on what you're trying to get out of your project.
If it helps at all, I think Blue Bear Sound actually has some examples of just what we're talking about here on his site.