o/
"Landing and ground battle on gas planet the same as terra" Imao sure? I think we need a little fix this and at the same time make ground battle more interesting. I suggest add GBB (ground battle bonus) for each type of planet. We already saw this mechanics in space battle - threater effects. It will make system with complex ground planets more protected for both sides. Just imagine ground battle in Vietnam jungle and in terra. Were is more difficult, lasts longer?
There is a table were we can see how successfully our army fight on planet (we need to check this for balance)

The basic key: the more difficult conditions the longer fight/capturing planet

Planet typeInfantry bonusVehicle bonusAir bonus
Frozen-25%-10%+10%
Cold-20%-5%+10%
Temperature-5%+5%+5%
Warm-5%0%+5%
Hot0%-10%+10%
Burning-80%-80%+30%
Barren+10%+10%+30%
Ice-5%+5%+15%
Acrtic-10%0%+10%


Toxic-50%-40%-30%
Desert+20%-20%+50%
Ash-10%-10%-70%
Lava+60%-90%-20%
Snow0%+10%-10%
Stepps+50%-50%-30%
Savannah+30%-30%0%
Arid+10%+10%+10%
Tundra+40%-15%-20%
Monsoon+50%-30%-10%
Medi-terranean+80%+40%+20%
Boreal+80%+30%+25%
Forest+150%-90%-70%
Terran+80%+40%+25%
Jungle+100%-100%-50%
Ocean-50%-50%+100%
Atoll-20%-40%+100%
All Gas planet-100%-100%-50%


All bonuses need to counted.
Example: system with Terran and Lava gave I + 140% (60+80) V - 50% (-90+40) A + 5% (-20+25) bonus for Both side

This make ground battles in late game more quicklee. Because a lot of plannet was terraformed.