I personally don't care for this name and it's likely that I never will. However, the spelling is at least decent. I wouldn't recommend this name but if it absolutely HAD to be used, I would implore you to stick to the original spelling.
I don't paticularly care for this name but as far as names go, I wouldn't categorize this one as awful by any means.
I just don't care for the sound in the middle. (TAHSH) and that it sounds essentially like a "mean girl's" name. (Natasha definitely doesn't bring to mind innocence) I think this is partially due to personal experience and partially to do with the name itself (how it sounds). On a somewhat separate note, I think that the Russian pronunciation sounds much nicer.
I think this name is very lovely. However, I really don't care for the spelling. In my honest opinion, 'Melanie' is just one of those names that looks better as is, with no alternative spellings.