As I've written before, I'd rather go for soft penalties to discourage stacking rather than absolute limits. Could even be pretty harsh, like penalties to attack and defense and collateral damage, no matter what kind of unit is attacking. My main objection to the 1 unit per tile rule is that it'll create annoying traffic jams especially if the units still have only 1 or 2 moves.
Civ1 style: when a unit is defeated, all units in the tile are destroyed.
Mixing with Civ3+, we have "whenever a unit is damaged, all other units in the same tile take the same percentage of damage".
This means that you can overlap units as high as you want -- you can even do things like guard knights with crossbowmen (to prevent pikemen from defeating the knights) -- but doing so for more than that narrow reason is going to be disastrous.
Ahriman said:
Ok. Unless maps are huge, it will have to mean that you can build radically fewer units available at your disposal.
Either this will mean:
a) Units take longer to build
b) Fewer turns per game.
c) You are forced to spend most of your time is spent building structures/wonders, not units.
These don't really sound like fun.
Or, my personal hope:
1> You need resources for units.
2> You need infrastructure (built in cities) to get resources
3> Building a unit is fast, if you have the resources to support it.
So you will have a mining city. It builds a basic mine which produces 1 unit.
It then starts working on improving the mine. Meanwhile, your high-population city with a barracks trains the unit the resources supply, and you get a swordsman.
That swordsman goes out and dies in war.
You replace the swordsman with another fast-built unit. This continues a few times.
50 turns later, the mining city has upgraded the mine. It now produces 2 iron, and you can support 2 swordsmen with it.
You'll note that you are spending lots of building time building structures/wonders, and not units -- but some of those structures are used to increase the number of units you have in the field.