The story maps are definitely meant to go from beginner, to intermediate, to advanced intermediate.
The current exchange maps do require a jump in skill. There aren't many, and they were made by very experienced players. I don't expect all exchange maps to be like that, though. And I expect some other maps to show up in inception that cover the spectrum of skill.
Story and Inception I can control, Exchange is up to everyone else. But in the event there is no happy medium for a given player, I included a random map generator in both PF and CW3. That was my thinking anyway. It was actually a bit of overkill to have a random map generator and a map editor with online sharing (took a lot more work), but I wanted the spectrum to be covered for potential players.
PF also has one more way to accommodate players. You can play with a sandbox fleet. A mission's energy constraints and enemies are still in place, but you could potentially make a mission easier (or harder) by using ships of your own design.
The final piece will all fall into place once I have custom ship sharing available (integrated in the game). That way a person could pick and choose from other people's designs when playing a map and not even have to make their own.