Ok, A couple of months back there was topic about FE10 hex editing referenced here.
Using the files from Fire Emblem Radiant Dawn along with DT gba de-compressor the files that could edit the game were decompressed and allowed for data hacking of FE10. The catch is that there was no way at the time to re-compress the file. So I decided to make a compressor/de-compressor for the Nintendo Wii and specifically FE10 and FE9.
The compressor will allow you to decompress those *.cms files that are in FE9 and FE10, edit them, and then re-compress them.
Also, included are Nightmare modules for the FE10Data.tpl (which is the name of the de-compressed FE10Data.cms file). The modules are for character and class data.
Nintenlord also has a compressor/ de-compressor that works with FE10/FE9, but this one is a more exact with the compression algorithm as well as faster.
The FE10 Compressor
FE10 Character and Class Modules