ugh.
"ship moves 2 and is now adjacent to land on both sides and then a land unit with 4 base movement moves 2 and goes from one continent to the other"
This is not a problem from a gameplay viewpoint.
From a flavor viewpoint the timing isn't a perfect match (ship gets there at 2/3 of the turn done but unit moves 1/2 of its movement for the turn afterwards which is more) but there is a limit to how much detail we can have without the players tearing their hair out from frustration so let's ignore that.
"'ship moves 2 and is now adjacent to land and a land unit with base 4 movement moves 1 onto the ship. Then ship moves it's thirds square, then the land unit disembarks'"
For flavor it's the same deal as before, the unit shouldn't be able to disembark.
However gameplay takes priority here, the unit has to be able to leave the ship because AI naval superiority is a thing. So this should be allowed too.
"ship moves 2 and is now adjacent to land. Land unit with base 4 movement moves 1 onto ship. Ship moves 1 and is now adjacent to another ship, and the second ship is adjacent to land. Land unit moves 1 onto other ship, and then moves 1 to disembark."
Again from a flavor viewpoint this is problematic. In addition to the above, the "standing" ship in reality obviously has to move between the first ship and the shore to let the unit move "through" it.
But from a coding perspective the second ship is not moving or carrying units, it's merely enabling that tile to be walkable for land units. It's no different than a piece of land. Even if I wanted this to work differently, I can't, but I also don't want it to.
Flavor, ease of understanding and gameplay requirements are clearly conflicting so we have to draw a line somewhere. We have to make an easy to understand rule. A unit can't be carried by two different transports the same turn" is such a rule.
In case of your cavalry example, we have no gameplay reason to allow it. It merely allows the unit to travel further, which we already deemed undesirable. Flavor clearly says it can't be done (turn ends for the calvary by the time the first ship is out of movement points. And finally the easy to understand rule also says it can't be done. So it can't be done.
By the way, if we want to cut down on overland movement in general, maybe we should consider having slower ships. Move 2 Triremes, Move 2 or 3 Galleys and move 3 Warships for example.
Windwalkers allow units to participate in battles and can move onto land so the gameplay argument that you have to be able to disembark doesn't exist for them. Which means there is no conflict of flavor and gameplay there so it works entirely as flavor dictates : when the windwalker ends the turn the carried units do as well. (ok this isn't entirely true, if the carried units were faster, they'll have movement remaining. We can't do much about that, the units might disembark somewhere halfway or only get carried a single tile in which case windwalk eating up extra movement of the carried units would make no sense.)
"ship moves 2 and is now adjacent to land on both sides and then a land unit with 4 base movement moves 2 and goes from one continent to the other"
This is not a problem from a gameplay viewpoint.
From a flavor viewpoint the timing isn't a perfect match (ship gets there at 2/3 of the turn done but unit moves 1/2 of its movement for the turn afterwards which is more) but there is a limit to how much detail we can have without the players tearing their hair out from frustration so let's ignore that.
"'ship moves 2 and is now adjacent to land and a land unit with base 4 movement moves 1 onto the ship. Then ship moves it's thirds square, then the land unit disembarks'"
For flavor it's the same deal as before, the unit shouldn't be able to disembark.
However gameplay takes priority here, the unit has to be able to leave the ship because AI naval superiority is a thing. So this should be allowed too.
"ship moves 2 and is now adjacent to land. Land unit with base 4 movement moves 1 onto ship. Ship moves 1 and is now adjacent to another ship, and the second ship is adjacent to land. Land unit moves 1 onto other ship, and then moves 1 to disembark."
Again from a flavor viewpoint this is problematic. In addition to the above, the "standing" ship in reality obviously has to move between the first ship and the shore to let the unit move "through" it.
But from a coding perspective the second ship is not moving or carrying units, it's merely enabling that tile to be walkable for land units. It's no different than a piece of land. Even if I wanted this to work differently, I can't, but I also don't want it to.
Flavor, ease of understanding and gameplay requirements are clearly conflicting so we have to draw a line somewhere. We have to make an easy to understand rule. A unit can't be carried by two different transports the same turn" is such a rule.
In case of your cavalry example, we have no gameplay reason to allow it. It merely allows the unit to travel further, which we already deemed undesirable. Flavor clearly says it can't be done (turn ends for the calvary by the time the first ship is out of movement points. And finally the easy to understand rule also says it can't be done. So it can't be done.
By the way, if we want to cut down on overland movement in general, maybe we should consider having slower ships. Move 2 Triremes, Move 2 or 3 Galleys and move 3 Warships for example.
Windwalkers allow units to participate in battles and can move onto land so the gameplay argument that you have to be able to disembark doesn't exist for them. Which means there is no conflict of flavor and gameplay there so it works entirely as flavor dictates : when the windwalker ends the turn the carried units do as well. (ok this isn't entirely true, if the carried units were faster, they'll have movement remaining. We can't do much about that, the units might disembark somewhere halfway or only get carried a single tile in which case windwalk eating up extra movement of the carried units would make no sense.)
