So, after some thinking ...
Why do we have "haste" as an ability in these card games?
How long does it take to cross a map? Trick question, maps come in many sizes.
There are maps where you can pump out 4 zerglings, send them to the enemy, and they are just getting the bunker started when you arrive. Others where the bunker is finished, and the marines are already inside.
In "Impossible Creatures", which actually had numbered tech buildings, you could send your starting tech 1 creatures at the enemy, but in most maps they would have the tech 2 building made by the time you arrived.
So a one-turn delay before attacking units arrive? Fits the "this is what we're modeling" for ground troops.
Which brings up the idea of "creature speed". What if your game was based around "most ground creatures have speed +1 turn, most air units have speed +0 turn, most ground units can return fire against fliers, and anti-air is relatively easy to get"?
Add to that an ability "extremely long range", maybe had by very few units, intended more as the "break" move against someone who walls up -- Starcraft has that in the siege mode (range 12, I think) and the guardian (range was something like 18?).
Now, add in your "map cards" -- tiny map, normal map, giant map -- as effecting the time for units to reach enemy territory.
You could use the "dune" model for attacking units. They aren't expected to return home. If you kill your target, instead of returning home, you move on to another target with no time delay.
1. Most units need one turn to cross to the enemy battlefield. Haste units do not. (Q: What to do about flying? For now, just say that the map is not a mountainous rock maze, and the extra time is just for distance. Fliers have the same speed rules. Can adjust later.)
2. Any unit can be sent to attack even on the turn it was summoned. Note that normal units will arrive next turn, while haste units arrive the same turn (matches the current rate of play/attack).
3. Attacking units that survive the first battle have the choice of either staying at the battle (to fight something else next turn, the enemy still gets to run production), or returning home (with the same 1 turn delay for non-haste units).
At the high level of play in games like StarCraft, or Warcraft 3, how do the players deal with "both of us sent units to the other side, and they met in the middle"? Are you micro-managing your combat, or are you busy with your base? How does it work when you're not at my level?