I tried to play a little with the ban on "rubber tiles" limit_units_per_tile. Before that, I removed three lines of code from the injected_code.c file (4423-4425). Everything works.
Here are the wishes for the restrictions:
1. Separate restrictions for each type of unit: land, sea, air.
2. An army is one unit.
3. Exclusion of workers (with an attack value of 0, or through lists for exclusion).
4. Exclusion of combat units that are busy building roads, railways and forts on a tile.
5. Skipping units passing further through a filled tile, without stopping them on the tile.
6. After a battle, a unit with HP 1/X can retreat to a filled tile.
7. Restrictions for cities (if possible, then depending on their size).
8. Cities can produce units in excess of the limit. These units can remain in the city, but once they leave it, they cannot return back. Or they must be thrown outside the city, except for stationary units.
9. Transport ships and planes with loaded units can enter a full city, but units cannot be dropped from transports in the city itself, but can only leave the city.
It looks as if there's quite a lot to sort out before it's really playable. For me:
1. Yes please, adds a lot of flexibility. Technically possible?
2. Don't care.
3. For gameplay you probably need, although does allow huge stacks of workers, which must take up some room, preferably an option.
4. Don't care, if they are also combat units they probably should count.
5. Ideally yes please, but could live without, presumably you just need to be one unit under the limit, so not so bad, if you move them one at a time. Would that work?
6. Could live without, if you can't retreat you get caught out seems fair enough. Also another reason not to completely fill a tile.
7. Yes, only really half done if you can store massive stacks in a city and your oppo can only attack with a limited number.
8. Needs fixing one way or another, again, a reason not to stuff every title. Could be missused to create big defender stacks if they are left in the city. Can summoned/produced creatures be delayed until there is room? Seems logical. A message would be useful, so you could move units out to make room.
9. Yep, although you can 'cheat' a bit by storing a reserve in transports to deploy after any losses, bet the AI won't think of that. Don't see an easy way to stop a player though.
Already wondering on what stack limit I would use! 15-30 on grassland? I hope/assume it will be by terrain type (if not that's my number 10, it adds a huge tactical change).
If it works this would change the game a good deal, big jump in the importance of unit quality, maneuvering and combined arms, over 'build a big stack of tanks/dragons'. Sweet.