Expand # of trainers in Emerald

Don't have an exact solution to your problem, nor do I know of a hack that has done this off the top of my head. What I do for this in the hack I'm working on is replace some of the match call rematch trainers with my new trainer, and then just repoint the trainer ID in that trainers script to make the second battle the same as the first, thus giving you a free, unused trainer. Obviously this isn't ideal and you might have already thought of it but it does work as long as you aren't trying to add a really large number of trainers. Hope this helps!