I think the following changes would be useful:
-Stars and planets don't occupy seperate squares, but rather a "system" takes the space of one square. One can zoom in on any system to view individual planets, and zoom in further on planets to view the planet and its moons, as well as their structures.
-Some more habitable planets house "minor civilizations," or civilizations that have yet to successfully travel to space. These civilizations can be dealt with in a variety of ways. Leaving the population unchanged will yield greater production; initial costs involve only building some modern structures such as Star Ports, and while build costs will be higher, so will production speeds by the same magnatude. Players can also exterminate the population, heavilly reducing turn-by-turn costs and chances of defection, but the initial costs are extremely high to transport colonists and build modern cities.
-Planets hold far more build space, and multiple civilizations can occupy a single planet, although such is extremely rare, occuring mostly in the middle of an invasion. Special deals can be set up to share a planets space, but civilizations are rarely inclined to sell more space than is needed for a port. By building a minimum of structures and paying a premium to make them difficult to find, a civilization can house useful structures without others knowing, but leaves the planet open for any civilization to publicly claim should they find it useful.
-Borders extend a certain distance from populated zones which the intergalactic council decides. Most of space will be empty and unclaimed.
-Carrier modules are available after the largest hulls are researched, and fleets carry many more ships. While players can send numerous ships together, they must be subdivided into fleets. Fleets could hold a few carrier ships full of smaller fighters; I should be able to send in a few custom-made Star Destroyers loaded with TIE fighters. When carriers are used, the speed of a fleet is not limited by docked ships, allowing for stronger fighters to be transported in a reasonable time. Carrier modules are expensive.
-Capturing a planet requires many more troops, and troops usually must occupy a planet for many turns to fully capture a planet. Any player can initiate orbital strikes if the correct ships are in orbit. Troop module costs will be balanced accordingly.
-Weapons, defense, and miniaturization are not part of the main technology tree. Rather, they can be researched indefinitely. Each weapons and defense technology a player researches acts as a trade resource, allowing any side to trade them with other civilizations without losing exclusivity to the technology. This gives powerful militaristic civilizations more bargaining power, and the technology itself more value.
-Civilizations will fear other civilizations with significantly more military power. More military power will encourage other civilizations not to attack, but if one or a few civilizations are too advanced other civilizations will panic, form stronger bonds with one another, and overreact to otherwise minor incursions. I know the current AI will be far less inclined to attack more powerful civilizations, but I don't think they'll worry if one civilizations holds nearly half of the galaxy's military power. A powerful civilization can releave much tension by trading their weapons and defense modules to weaker civilizations.
-Line of sight (LOS) will be slightly greater, and contain two layers. The first layer, the smallest, can detect anything. The second layer, which extends further, can detect only large objects, like anomylies, moons, et cetera. The second layer can detect the quality of planets. All star positions are still known from the very beginning, and planets are revealed a little later. The minimap will use 4 shades of gray to illustrate explored areas.
-The AI will, of course, be even better than it is now.