I think a better solution might be to allow building the cargo landing pad anywhere, since you can only place one of those on a surface.
Obviously you'd have to make one and ship one to start, but I think that allows for the least amount of cheese potential.
As for rail supports, there was actually a bug where they would almost always explode no matter what, even when they're connected by elevated rail.
I've also fixed that in version 0.0.4, that way you should still be able to get rails to another island.