Perhaps replace the old training room style with the combat pit entirely? Gold cost is now more hazard pay for your creatures, also makes training less passive and forces you to manage when you want to train and when you want your creatures to do other things. Also adds value to prisoners as training fodder, and adds risk to training, as if you train an the wrong time you could suddenly have a battle on your hands and a large portion of your population is injured from training. I know the training room is kind of iconic for DK, but I also want to check myself to see if I accidentally have my rose tinted goggles on. Coding for either shouldn't be too big of an issue, so it's more a question of style and feel.