Sorry for the confusion: the issue of the game hanging on a black screen when loading a stage is also present even when the spoiler-ed code in the above post is the only thing being patched to the ROM by EA. (Not #include-ed as part of a larger buildfile.) If the syntax in that code looks good to you, should I conclude that that modification is just not working? Thanks.
*Edit: maybe it's these .asm files in the "source" folder that was distributed with the mod. I wonder if something separate has to be done with these. It's not in the readme.txt, however. This is probably not worth spending more time on. It would be a neat feature, but I can live without it.