I Like the Socket System System we have, just as the OP said though, There needs to be more Things to Socket in and Out.

the terrain of a map is constant.
as part of this terrain map, there are fixed "sockets" with different sized. small medium and large.
ideally the map should randomize itself on every new battle and place random outposts (buildings) into the sockets of their appropriate type. this would make it feel like you're in a different district every time.
because each of the individual outposts has been balanced as its own self-contained mini level, and the terrain and its sockets are balanced in terms of distances and hills and stuff...any map made with this system is GUARANTEED to be balanced.

right now it's much more static though.

here's how you do planets to make them interesting and dangerous

ice planets; movement penalty on everyone due to extremely frigid temperatures and driving winds. combat would probably be slow and trench-warfare-like.

lava planets; big lava pools can be put in sockets on a map and occasional eruptions rain down lava balls which can kill most infantry or mess up a vehicle. the heat might cause mild armor penalties as well since the plating might not perform as well in high heat

storm planets; the entire planet is a category 7 hurricane all the time. intense winds push everyone in one direction for the entire game if they're on slick surfaces like metal or pavement. dropships get blown off course very easily, infantry need to carefully move around, and tanks can get slowly blown into walls. the entire sky is FULL of lightning but otherwise it's pitch-dark, so the battle resembles a rave.

plasma planets; big arcs of plasma appear and slowly move across the battlefield causing huge shield damage on anything they arc across the terrain. they're slow and easy to avoid but can cut off certain areas. the sky is aglow with plasma. your HUD has a mild static effect from interference and being near the plasma arc makes this far worse. this also plays havoc with the minimap. battles on plasma planets are beneficial to those that don't rely on their hud

ocean planets; takes place in small, cramped underwater dome districts. tends to be much closer quarters with lots of cover and ambush points. compartments could flood at random perhaps. no vehicles

moons; generally out in the open, maps can be pretty sprawling. Low gravity at all times, might be difficult to get used to at first. Staying in sunlight slowly drains your shields due to no atmosphere and direct solar rays. NO SOUND except music and maybe a very dull thud from your own gun firing due to bone conduction, as well as your own breathing rate which goes up and down with the action.


temperate planets will take up the majority of planets you fight on. the above are more like novelty worlds that occasionally pop up on the rotation to keep you on your feet.
and if a corp has built their armada in such a way that they have a home-field advantage on one of the above listed worlds, all the more power to them if they take one for their own

Add to Plasma planets shield penalty.
Since Lava planets get armor penalty.

Shields are energy based so it's logical.