I'm curious what that mod does that's different than the built-in developer mode. I've been tinkering with airport creation, here's what it looks like in-game, pretty much the same as that mod.
I'll have to try it out. My main problem is that I'm trying to make a simple dirt airstrip, which looks fine from the air, but when you get on the ground the "default grass" overrides it making it blend in with the surroundings and just generally looks bad. Asphalt doesn't do this, it knocks the grass out. If I could solve this issue, I think I could make some small sceneries/airports that look decent. Here's the grass issue I'm talking about:
Looks fine from above
Blends in with the surrounding at ground level