What pokemon to use for a solo? Hmm, this is a good question...
The mudkip line is the one I literally uses for everything, but I am not sure about using one unless it is taught an ice move. Dragon types are another good choice, I think all the games I've played have something ice at some point, so I am not sure about that either.
I'll probably choose something I like in the end, because it is much more fun than trying to decide on a balanced pokemon. It will probably depend on the game I am playing and what will I face...
As for dig vs. escape rope... If I have certain ground types, dig. Otherwise I choose an escape rope.