I think it would hurt camming as a whole. The diversity of models is a huge selling point for members, giving them an option to shop around for the model that fits them perfectly. Having such a system wouldn't have much financial benefit to the camsite either. Sure, it *might* help with keeping models staying on the site and not moving, but it would also prevent other models from other sites that want to switch over and bring their fans with them from joining. Any model that retires completely due to room counts will likely just have her (by definition few) members move on to other models. Having such a system would likely drive many old members away due to the site becoming stale.
Not to mention how high that number limiting models would have to be. The rate that new models retire, or join and only broadcast a few times must be staggering. The site would probably end up losing all it's models quickly. If it's too high then the system would end up being redundant and barely help the existing models at all.
Also I'll be honest, 25 viewers after 2.5 months doesn't even sound that bad. I've seen models that bust ass for years and are amazing at their job struggling to keep that many in their chat.