I'm not even sure if I understand your question...are you asking if you can delete some TBP files so that you can save space, while still running it out of the original FS2 installation?
If so, no - since TBP is standalone, I'm pretty sure most of their files have been replaced by new ones, and removal of these would cause problems.
If you don't have the original FS2 installation, and only have TBP one, you're going to have to have the original FS2 so that you can play it. You can download it off of Home of the Underdugs, or by looking into one of the Freespace forums for the full download (try General Freespace, that's where it is, IIRC).