Yes
I have never done what you are suggesting, but others have.
The ideal way would be to search through the files, and see where the Firefox home pages are listed, and change that file. You may need to change more than one file.
A place to begin looking, would be:
firefox/usr/local/firefox-official/defaults/pref/firefox-branding.js
firefox/usr/local/firefox-official/defaults/pref/firefox.js