Taken from the game Conquest of the New World.
In CNW you had a grid of 2 by 3 or 4 by 3 can't remember with two squares on the end for you and your opponents flag square.Armies consisted of infantry, cavalry and artillery.
There were generals which based on their level of experience would allow a certain number of action points to your units.There was a unit placement phase before the battle began.
You would move units up or to the side with combat happening when either cavalry or infantry was in an adjacent square.
The goal was to capture the flag.
There was bonus for flanking and in the case of cavalry charging.
This might put a little more strategy into ground combat without overcomplicating it.
Ground troops for infantry.
Mechanized armor instead of cavalry.
Could still have artillary.
Would fit into the possible hero system for leaders to infer bonuses to units
Ground tech could be derivative of space tech i.e. mass drivers, beam weapons and missiles.