Quote Originally Posted by Monkwarrior
This is only a possibility, not 100% sure.

Have a look into the file export_descr_sounds_prebattle.txt

There you have several files assigned to different cultures. Perhaps by changing the assigned files to the egyptian culture from Arab_Generic_01.mp3 (etc) to Greek_Generic_01.mp3 (etc) you may change the speeches.

Good luck.
YAY! It worked! My prebattle speeches and battle voiceovers now have a greek accent. Time to start my first Ptolemaic campaign, methinks...