Em, no problem - same as Gmajor (just one sharp). Bmajor I can't even contemplate!

Back to Eflat and Bflat -
"Classically trained violinists would have no trouble with the fingering, but in my experience, they would have difficulty playing without the dots in front of them."
Not necessarily true. Most non-classically trained fiddle players play mostly in D and G and perhaps A and the related minors. All they have to do is start playing some "flat key" tunes and their fingers will soon know what to do. It's just a matter of doing until it becomes just as comfortable as D and G and A. Then there's no need for the dots, it's in your fingers.

As for singing, I'm also a singer and often prefer the flat keys for my vocal range (baritone). So I can easily transcribe many songs that I also play on the fiddle into those keys, without any reference to the dots.

Cheers, S. in Seattle