Was thinking about this. in STO, the universe is a small world. Literally.
Call me wierd, but I want to travel for hours in the vast openness of space. Seek out new life and new civilizations. That being said and this being STO - will prob end up blasting craters in their homeworld.... but anyways...
My thought is this... why can't you string together star cluster. For instance you have the Delta Volanis Cluster. If you fly in there, the first map is relatively easy. Then you fly to one of the other 3 sides. As you go in, it gets a little tougher, and a little more tougher, and a little more tougher as you deeper and deeper into the map instances.
At some poin, you reach 'known' space. From here the system goes into a variable system that is independent of your rank. You could be a lieutenant and fidn yourself battling an enemy that is the equal of a RA, or be an RA and find the enemies to be pathetic worms ripe for slave labor to build you new summer villa