Complex sentence: The Augment System was devised to replace the system in "Final Fantasy IV Advance" where the characters that were temporary in the original version became playable again at a certain point, as the developers felt that this system changed the game too much.
Split into simpler sentences: The Augment System was devised to replace the system in Final Fantasy IV Advance where the characters that were temporary in the original version became playable again at a certain point. The developers felt that this system changed the game too much.