This has more to do with tight coupling in general, and I agree.
I went down the path of trying to rewrite radiant my moving the page spec and page model only to find that things were so tightly coupled that I had to bring almost every other model along.
First things first, we need to rearrange a lot to get the app working with Rails 4. It is definitely due for an overhaul, but getting it working on the main platform is the goal. Making it more modular is a major task in itself.