Oh, i forgot, territory issue, im fine with the DW map feature, but here is an idea, could be added as a option so you can select it, and this reminds me of STARS! the game old but still have it in my machine, even so the game was plain dots and you only see the scanners range, graphical challenged, but difficult to pinpoint each different empire, but with a mod made for the game, you could generate a map that shows you each empire, the dot as the planet, then the sphere with a color for each power, if i can get my CD's i will show you a picture for an example.
But my idea is that, each empire has a sphere of power, and influence, lets say, planet Omicron, colonize it, (Im using the pixel method as in distance from the planet and out, not accurate but an example so you visualize how it could go) it gets a small sphere from 20 pixels to 40 according to the growth without a military ship present, but with a military present on a colonized planet, it could start same as the planet from 20 pixels or whatever size the sphere is, one ship could add a pixel, then two 4 more pixels, and if you have a fleet of 9 ships, the sphere could reach to 60 pixels and the game has a maximum of 80 to 100 pixels.
But if theres another power nearby and the sphere hits yours, many examples can be made, lines for example red and blue crossing in the sphere could be seen indicating a mix of power, or dots instead of lines, or like in the game i mentioned, if i remember, the sphere tends to consume my enemy until i had a huge presence around it only the dot could be seen identifying the enemy when it lost everything and i just got no time to invade it and having the planet for myself.
*That* is the exploration that awaits you. Not mapping stars and studying nebulae, but charting the unknown possibilities of existence.