To save the model with _external_ textures, while ignoring the textures and their formats, is absolutely sufficient, IMO.
I guess, when you save the model with external textures, there is only the path to the texture that you save within the model.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt