While I generally like the idea it is important to also think about what happens when that server becomes bogged down and starts performing poorly. Are you going to do a scale out (add another server connected to the same set of SSRS databases which is only supported on EE) or a scale up (add memory, CPU basically) or what I like to call a poor man's scale out, add another server that has all the same reports/datasources but you have to maintain them manually. With two servers you might consider the use of some kind of load balancing.
It is also important to think about licensing. If you install SSRS on another server you have to license SQL for that server. When you license SQL you are licensing a machine effectively not the individual components. The same is true if you install SSAS, SSRS, SSIS, and the engine all separately you would need 4 licenses.
CEWII