[GreyHat]

One thing you could do is recompile the WPILibJ libraries from their sources including your utility classes -- although this is a fairly dirty solution. You'd have to distribute the library to those wishing to use it and have them add the libraries to the cRIO. The issue with not being able to add libraries to your project is that the platform on which it runs, the cRIO, is a static platform, and won't have extra libraries. I'm not sure if there's a [non hacky*] way to add a library that is assumed to be on the cRIO. In the end, there is no easy way to do this, unless you want to distribute sources.

*You could use a ClassLoader and reflection to access classes from the library, but then all end-users would have to take a similar path.