Those optional dependencies are mentioned in the info file and I left them out on purpose since folks tend to stick with one format of encoding, or at least one at a time. Since the default method of TC is to run in RAM, I prefer to keep RAM use low and let the user decide on what is to be installed and not force the installation of files that may not be desired or needed. If an app or lib is a mandatory dependency, I put it in the .dep file. If an app or lib is optional, I like to keep it optional and mention that option in the info file. This approach was used with XMMS as it does not need ogg to function, but needs the ogg extension to play ogg files. So ogg is not in it's .dep file but is in the info file. Some folks may not use ogg and therefore may not want it installed.
Thanks for bringing this up and I hope you understand my reasons behind leaving optional extensions optional. I know this is a different approach than with most other distros but we also have different goals.