Thanks for all the feedback.
As for invisible units, that is a good point, Dale. In concern to cities falling easier, I would have thought of two solutions for this.
1) Have a city tile be able to hold 20.
2) Train the AI to not only turtle inside thier cities but also in all adjacent tiles to the city. (90 units in 9 tiles.)
Or both, which would result in a max 100 units in a 3x3 tile box around every city. This would put an end to stack of doom making an invading force of 50 units be in 5 groups. (Alot harder to do multiple collateral damage to every unit coming in.) This would mostly fix some problems I have with AI invading armies being generally easy to collateral.
Also, how will new builds be handled in a city with 10 units already?
This one I do not know about yet. The only thing I can think of is to have it "pushed" to the nearest friendly tile available. Like when culture expands or open borders are cancelled.
If a unit has a path through the tile, does it have to wait or will it go through the tile and continue?
The unit already having a path that gets interrupted by zone of control I would like to have the path be negated. and the unit is active needing orders when the turn reaches you again.
What about cargo? Is it counted? If so makes fleets useless, as have two fully loaded carriers and there's 8 of 10 units with no battleships or subs. And you couldn't have two loaded transports in the same tile either.
This would make cargo ships be wisest to only have 1 per fleet. So, a full transport is 5/10 and a full carrier is 4/10. Then you have 5-6 other spaces to put in subs, battleships, destroyers and such. A carrier is a poor choice to guard a transport anyway so I see no problem with the inability to stack full sets of these as you actually could and still have rom for a battleship as well. Also, 1 tile (10 units) is a small fleet. A large fleet will consist of about 2-4 tiles. (15ish-40 units) So 1cargo unit per fleet is ideal in this idea.
Of course if I could, I would prefer to have any "cargo units" be assigned as "temperary invisible status" if I could. This would make sense as the carrier would be the same size whther it has planes on it or not. Same with a transport.