I would which for a strategy game that would be like a mix of Europa Universalis and Civilization with a tad of Total War in the strategic part but featuring not only a single planet but hundreds of them, and their respective star systems. A turn based strategy game.
With Total War like battles for land and sea battles and Homeworld like battles for the space ones. Or real time tactical game.
With a research system akin to the one of Space Empires V and overall feel of Emperor of the Falling Suns. Where population and resources are taken into account in a local way. No magic piles of resources, if you have steel in one side of the planet and a vehicle in the other side or even in another planet, there must be a way of taking the steel from point A to B.
Oh and with a custom array of design for infantry gear and vehicles load out, but also even buildings and races themselves, like Spore but not aimed at 5 years old, something serious looking. Where in the case of vehicles each design really affects it's performance and fire arcs and such. And borrowing a little from SotS where prototype vehicles have more cost and some vehicles are really nice while sometimes others are kind of lemons. As you progress in technology new types of components, hulls and vehicles are available.
As for the infantry, you get to not only choose the uniform and weapon load out, but can make several types of infantry and then the squad, platoon and company load out. For the individual soldier imagine something along the lines of the Dawn of War army painter but with the Firestorm Over Kronus mod weapons choices, but instead of just painting you choose which weapons they carry and what kind of uniform they use for desert, urban, ice, jungle and so environments, the weapons they will use and their combat behavior. Also while at it, as with the vehicles, you get more things as your tech progress.
As with the infantry squads and companies system, an army and fleet load out system should be used, so instead of you needing to recruit everything individually you can have an template and recruit whole armies and fleets on the whim of a click, the game recruiting and commissioning the vehicles from the nearest/most suitable/convenient planets, factories and shipyards.
And last but not least, a proper naming system for ships, where you can customize if they get random names (from generic or custom lists), numbers or both, and their class and design type are also made clear and if any or all of this is written on the hull or not, where the first of a class can auto get it's class name if you choose to. The same go for army naming, specifically for squad, platoon and company levels.
Graphic wise I would not be much concerned. Something along the lines of Dawn of War level of graphics would be nice but I would be happy even if is something in 2D, however I have heard that even when 2D is less demanding to the machine, quality 2d graphics (Starcraft 1, Age of Empires comes to mind) are actually harder to make than 3d.