This is true, and a scenario editor should not be too hard to slap together. Even I could write a decent one, but it would take me a couple of weeks to do it well. Besides, I hear Tanone is already working on one.
However, if you like the IGC, version 1.8 includes a utility to select playable nations. The new version of this utility (to be included in IGC 1.8b or 1.9) boasts the ability to disable/enable many of the most popularly demanded options. (A free Ireland, Holland, Norway, various COTs, etc).