I now have the basic infrastructure to load file splitting strategies using MEF. Here's a screenshot of the split by line strategy selected in the UI:

So, with a bit of C# programming, you should be able to create your own file splitting strategies.

I got the basic functionality of the file pattern tokens dialog done. I added one more feature that I still need to implement. I wanted to give users the ability to type in their own file names, so that they can see how the file pattern will affect the file name. Here's a screenshot of what I have so far:

I'm hoping to have most of the file splitting stragegies on version 1.5.1 implemented before Christmas.