Understood.
So... isn't it much easier and more understandable for both modder and the player to not let the infiltration battleship land at all?
(same as it is today)
More understandable? I didn't think so. I assumed destroying the UFO in
ANY way would trigger the interruptPercetage, and I had to read it very carefully to realize that isn't what happens.
Easier for the modder? Not for me. I'd have to take into account how UFO landing affects your ability to interrupt the mission, and try and figure out a strategy such that the player can achieve the end result (thwarting alien ships = thwarting alien plans) without having the slightest clue how the whole thing works internally.
Easier for the player? I don't think so. In many cases the alien ship has landed by the time you have arrived on site. Plenty of them will take off and land again, in fact that might be the norm rather than the exception. If I were playing your mod and you told me that I will always prevent the alien base from spawning if I shoot down the final battleship (on base or infiltration mission), and I arrive just in time to see it land, I'd expect an immediate ground assault to make the mission fail and prevent the base from spawning. In fact when I was newer to the game, this was indeed what I expected to happen. With inferior interception capabilities, I would be sending transports to intercept every ship on the ground. I didn't understand why they successfully made an alien base when I hadn't allowed a single ship to complete their ground mission.