That buff system sounds pretty simple. The jass part you sent me is, uhm... not that great though. I can't tell how well it works, but in it's current state, you might aswell have made it in GUI altogether. I think the errors you get are because the global variables are not copied, make sure you set that flag in the editor settings where it automatically copies missing variables. There are also some in the jass section, which won't be automatically copied - these variables are named "unit", "id", "integer1", "integer2", etc. They are totally unnecessary though, as you could easily use locals instead (i can fix this for you). Adding conditions for blight ground seems pretty easy though, i can fix that later today if you want.
About the parachute spell - what i meant about specific demands was more like: "how do you want to use it"? Can i use vJass for it? I can assure you, that using it will be very simple, even for someone who doesn't know jass. Out of the top of my head, i imagine it like this: you call a function on a unit which basically causes it to start parachuting. It will instantly be set to a preset (or choosable?) height from which it will slowly drop while displaying the parachute model. It will be paused for the whole process until it lands. Does that sound good to you? In this particular case, the parachute model would be added using an ability, as i don't think teamcolor works if you add it through triggers (unless this is a tradeoff you can accept).
The airplane system can be used with any kind of attack. It can even use spells. Think of it as a normal unit that just happens to be constantly moving forwards.
