Yes, that should work, decals are quite effective, as also are detail textures, slightly displacement alpha changes, detail sprites, even normal maps. There are a lot of techniques to reduce tiling. Using good quality and high resolution textures for ground terrain is also basic to prevent tiling. Regarding memory requirements, all those texture techniques scale well on this engine, is not a big problem. My concern is about displacement resolution needed to make terrain not very bland, and then brush work, and of course: lightmap scale needed. Lightmaps would need more texels to look like 1:1 maps.
You could do trees with really aggressive LOD at the expense of memory requirements. Full detail within maybe ten feet, falling off to much lower polygon approximations beyond that, and down to maybe two intersection polygons (forming an X from a birds-eye view) from over one-hundred feet. Like I said, though, the memory requirements tend to go up when you do stuff like this though, as the model size is larger, and if you want a forest that looks good you'll need several different tree models, etc etc.
I seem to remember reading somewhere that forests aren't feasable in the Source engine, something about overlapping alpha channels. I think this is fixed in Episode 2 though.
The z-buffer in Source is reversed for overlapping transparent textures, yeah. It seems like something they're bound to fix with Episode 2. But of course, that's been delayed to near-fall, now. Either way, Adam Foster will be pleased when that is fixed.
as far as I know Source just enlarges the skybox with a factor of 4, so x16 skyboxes need to be 4 times smaller than x16 (this is confusing me so early in the morning)
The sky_camera entity has a property which determines what scale the skybox is at. Read more about it here.
ah I got the 4 from a tutorial on that wiki site :/ anyway doesn't matter. The skybox will be smaller anyway.
from my undertstanding, 16x maps are just maps in which all empires models are scaled down... nothing different would need to be done with the 3d skybox.
The skybox will remain exactly the same method to the best of my understanding. The scale is defined by the mapper though, so I can't see why a box any bigger than 4x would be neccessary, unless you had some seriously large visibility. Yay! No more fog!
I'm not sure if this has already been said but what will happen with the maps right now? will they be moved to x16 scale or will there be a separate models for the current size?
There is a mod called Eternal Silence whose ONLY map uses this method to create the illusion of flying into outer space between two motherships. They do it well, but there are occasional problems. (Ex. Once I actually lag spiked and flew into outer space while I was not in a ship and I looked up and about 5 meters above my player model were tiny spaceships buzzing around flying around my head. They couldn't see me though. I thought it was hilarious, but never got any Screens of it.)