First off, you do not have to use a Toad Charge at all. There are other folks on these forums that would tell you that, if I hadn't done so now. That said, I did use one in my installation.
Secondly, depending on how your coach is wired (speaking for "wyorancher" here), you may need some form of diode between your coach and toad, to prevent feedback of 12V from the toad to the coach circuits. The Toad Charge does provide that function, but so does a diode by itself.
Now, to your question. The circuit breaker is there to protect the wiring from starting a fire should it short to ground. It's supposed to be installed as near the battery as possible. You should not move it to the toad. The charge line must be fused or have a circuit breaker at each end to be safe.
What you want to do, which is use a charge line that may already be in your coach's wiring, is a great idea, and my preferred way of doing things. If your coach has a charge line (you say it does), then you should trace it back to the battery. On some coaches there's already a circuit breaker or fuse in the charge line, near the coach battery. In that case, you have the option of installing only the Toad Charge itself, and not installing the circuit breaker or two-conductor wire.
In a prior post
I discussed the 2005 Kountry Star wiring diagram, but I could not conclude that a properly-fused charge line existed. Perhaps you will be able to trace it out and confirm that one way or the other.