Hi Chris,
If you are owning a Premire Pro license, then you might probably use Adobe Media Encoder. This works well if the source files already have the desired channel setup (24 or 32 bit respectively), and thus you don't have to merge fill + key files. But if you have to there is no way around XPression Video Coder (or try for the right programmer as you suggested ;-))
Regards
#XPression