Embarking, but only in ally territory?

[679x]

I'm trying to make a custom civilization that has the ability to send land units onto water tiles without the required technology as long as the unit is on or near friendly territory. First, is this easy to code? I then realized after thinking about this ability that this may not work the way I want it to - could a unit get stranded in the water if it strays too far from allied territory and loses the ability? For example, if a unit enters the water in a city's borders, then travels through the water outside the city borders, will the unit then lose the ability to traverse water and then get stuck in the water, unable to move? Will the unit instead get kicked out back into a nearby land tile? Will the unit simply be unable to move to the tile if it wouldn't be able to embark there?

If someone could make an estimate about what might happen, that would be great, before I spend the time to figure out how to code it, haha... thanks

 

[NicoML]

I don't know about modding, but this it's interesting, also you have to think about desembarking. Supposing that the unit it's abble to embark only in friendly territory, travel thought neutral and/or enemy naval territoy; they also have to be able to desembark, at least, in neutral territory.