I've built a couple of Swamp Ash strats and played others and the tone just never has worked for me. There's always a 'softness' for lack of a better word.
I've read that Stradivarius et al soaked their wood for years before drying it. So that seems to imply that Swamp Ash would be great since the only thing that makes it 'Swamp' is the fact it was grown in swampy areas and the lower parts of the tree are soaked/full of water. I don't think they're even supposed to use the upper, non-soaked parts of the tree. But this for a solidbody guitar not a hollow violin.
If you can get Sassafras you might consider it. I think Pine is often under-rated too.