"if you just play the same fingerings as a violin, you are a 5th lower. ie, Key of G turns into Key of F, etc. The back up players will love this."
This is not right. - a fifth lower means that the key of G becomes C, D becomes G, A becomes D and E becomes A.
So, all in all you have the same common folkie keys as on the violin with the addition of a lower C major and minor, and a lower E minor. To play as on a fiddle you just need to move the fingering up a string.
I prefer the viola for song accompaiment, not just because of the lower range, but because of the richer sound when playing in the same registers as a fiddle.