Hi tsentom,
I had a suggestion for you and your Python wizardry. You mentioned that you often use these new promotions for your UU's. I don't know if this is possible, but wanted to put it out there.
I use the Longship as a second UU for the Vikings in my mod (you may use it too, I don't know). I was thinking it would be cool to have a promotion that would bring back the old Civ3 style of ocean exploring. It might work best for a promotion unaccessible by other means.
For instance, the Longship could have this promotion and it would allow it to venture into Ocean squares but with x% chance of sinking every turn. This could give the Vikings a jump on colonizing but not so overpowered as just letting it explore Ocean squares.
Let me know what you think.
Cheers,
ripple01
Basically this has two abilities.
The first is a pre-caravel ship going into ocean. There's two ways to do this. It is possible to do so with python (and thus as a promotion ability) using the unitCannotMoveInto function in the GameUtils python file. The problem is, unitCannotMoveInto is one of those functions by default turned off and turning it on makes the game run slower. If you don't mind this then we move on the the next step. Otherwise, the way to do it is to give the specific UU the ability to go into ocean in the XML (thus can't have it as a promotion).
The second, the chance to sink in ocean tiles, is relatively easy. Basically it uses onUnitMove in the EventManager. First a check for the unit, then a terrain moved onto check, then a tech check: if you don't have astronomy do a random number for the percentage you want, finally if it fails the percentage then kill the unit.
So basically, it is very doable if you just make it a UU. While possible as a promotion it's not really recommended. However, I'm unsure how the AI would view this. They wouldn't understand that the ship has a chance to sink -- and I'm unsure how to make them aware of this.