To Arthmoor: here's screens of how the snow box looks in the CS: the first shot gives an idea of http://i285.photobucket.com/albums/ll61/Revanchism/Particle%20Effect%20Resources/Nosnowcollisionnecessary.jpg, the second is http://i285.photobucket.com/albums/ll61/Revanchism/Particle%20Effect%20Resources/One-windowexpandedblizzard.jpg by the mesh as it is right now.
I think at this stage I'll send you the current mesh and you can tell me what needs changed for your needs. I can adjust pretty nearly anything you like about the system (hmm, am I going to regret saying that?). Unlike the bubbles effect mesh you don't really want to be scaling this one in the CS, tiny or giant bubbles are one thing, tiny or giant snowflakes are a bit different. Just tell me what adjustments you need made and I'll handle it. After you're happy with the effect, I'll see about optimising the system as best I can.
Vac
Edit: to Ibsen's edit.
What's the problem with the size of the creature files? I spawned dozens and dozens of them simultaneously for performance testing and didn't hit a problem (AI seems to be more of an issue). From the distribution point of view, because it's just text data for the particle system and not meshes, the nifs compress stupendously well. The entire VASE resources compressed to under 3.5MBs.
Edit2: Anyone else who'd like access to the WIP snow box mesh (I'm thinking of house makers here) can PM me for access to the file. I need feedback on how to make it better for making it look like it's snowing outside your window.