Changing text won't really help in this case. Currently hex editing only will change scripts. Find the script that triggers national dex mode and move it so you somehow get N-Dex early. (I've never tried this before so I'm not 100% sure of script.) NPRE can help you view scripts.
Use a program like GIMP to limit the color pallet after you edit the image. Ensure that specific image has a total of 15 colors. Also, when you said "before" and "after", do you mean pallet before and after, or does the actual image change?
If you use KazoWar's BWTE, the trainer ID box should include the names in the correct order. Copy all of 190 into a text-editor, and compare using line numbers (n-1).