Great times for sure!
I'd love to see an 'impossible zone', but there would have to be some conditions:
1: Not every mission is super-difficult, but there's a random chance of 'wrong intel' at the contract selection board.
You jump in expecting 1 fairly tough way point and the kitchen sink bounces off of your windshield instead. All the other 'normal' waypoints would still be highly challenging though.
There could also be 'emergency scramble' mission offered on the board. For those you would know what to expect.
2: It would have to be a forward-outpost close to Vonarion space, and you would either have to take the long way, or brave the shortcut + some autopilot time to get there.
3: A general location marker for the zone would only appear on the Quadrant Map once Legend/FADM rank was achieved. There would be no sector coordinates given, just a general area to search. - top secret stuff and all that.

Whether one treats new or unranked pilots to the info once they get it would be a spoiler, but at their discretion.
4. Lose missions = lose rank points for mil. rank. Lose your FADM rank, and no more contracts offered from the secret base. Go back to the main zones and get your points back before you try again.
5. Players with less than Legend/FADM rank wouldn't link to full ranked pilots taking missions. There would be no waypoint set for them. Only Legend/FADM pilots would be offered missions from the base/carrier in the sector and link for co-op. Lower ranked players could be there, but they wouldn't get any missions offered. If they did follow an on-mission player to the waypoint, they would be able to fight, but wouldn't benefit from a mission completion. High-end loot (if any was dropped) would be the only reward for lower-ranked tag-alongs.
Well, at least that's my opinion....
[Edited on 5-4-2014 by Rubber Chicken]