If the artist changes it, thent ell them that's not what you want. It's YOUR skin.
Personally I like the sketch. I'd ask the artist how it would age, but I think the other posters are correct in that you can't drop the size tons without losing the details.
I think it would make a very nice tatt, and the artist should be able to almost trace your sketch, and reproduce it in a tattoo design very easily.
If there aren't decent tattoo artists in your area, drive. It's worth the effort to get quality work when it's going to be on your skin forever.