More WIT Research:
Brawl WIT-modified file size limit? (Needs more testing)WIT
has the ability to increase the size of an .iso. There may be a limit to this however somewhere between 9,548,640 and 9,603,872 KB (I'm on Windows so 1KB=1024 Bytes). Once the limit is passed, Dolphin fails to open common*.pac or boot.pac for unknown reasons.
Additionally, the limit of a .wbfs file compiled by WIT (for USB loading) appears to be lower than that. WIT will fail to compile the .wbfs and complain about the WBFS limit. It'd be helpful if the WBFS limit was defined somewhere...
Practical application: Every character will need a .pac and .pcs file for P:M All-star mode as they are now treated as transforming characters. At 100 movesets with almost 15 costumes each, having the .pac and .pcs files for every costume isn't feasible without SDHC support (which Dolphin lacks). I was hoping to transfer my entire fighter folder to my .iso but it appears to be too large (custom music also takes up a lot of .iso space and my dummy files have been deleted).