Karl, you may already know this, but each .gcode file has an estimate for the total build time at the bottom of the file. We will look at maybe parsing that information at run-time and using it to predict build time remaining, but that at least gives you a way to make an estimate right now.
And we actually had a G-Code editor in the program at one point, but it had a tendency to be very slow with extremely large G-Code files. Try to open a 30MB text file in notepad and you'll see what I mean
Speed is a big part of the pleasant experience using the Creator software so we're trying to keep that a priority.