Alright, here's what I feel on the subjects:
1. Particle system:
Terranim8or already makes particles possible. Yes, it's an external application, but no, it's not difficult to use. If there's already something that can do a good job of particle animation, I don't see why Steve would want to create the same thing in anim8or when there are many other requests that aren't in any way possible yet.
2. Built in UV mapper. To me, this is the same thing. Yes, a built in UV mapper would be awesome. Perhaps Steve will create one sometime. But as of now, there's external applications [http://www.sharecg.com/v/5169/software-and-tools/LithUnwrap---Free-UV-Mapper-for-Windows]Lithunwrap[/url], which I feel to be one of the best freeware UV mappers,
UVmapper which it seems you already know about, and I hear
Wings3d has a nice built-in UV mapper you could use. There are also plenty of tutorials on these different applications (they don't have to be anim8or specific since they're external programs not relating directly to anim8or.)
3. Splitting screens: I'm sure this could be done. I do kind of like the idea. Such as, when I want only two screens instead of four, since four can slow things down a lot, or give me a very small portion of the model to look at.