From the obvious and probably-already-been suggested department, how about a machine that accepts UU-matter as input and can output a specified amount of a specified material? For instance, inputting one matter, taking one piece of wood, and the machine retains a 87.5% "charge", since normally you get 8 wood for one matter.
I think one of the arguments against this in the past was the supposed "secret" nature of the UU-matter recipes, but here's the issue with that: All the recipes are right there on the bloody Tekkit wiki, so the situation we have here is annoying noobs having a better idea of how uu-matter works than actual IC users. I really don't think that secret thing is serving anyone, and having a convenient way to get stuff from matter would be pretty awesome. You could even skip matter entirely and have a target-item function like the EE cheat machines on the mass fab.