AMS: "generally the base OS (Windows in this case) is the one that will be used and whatever apps are associated with that"
Only if the two are equally good at every job. The whole point of using VRPC is that people want to do certain things in RISC OS rather than Windows.
You are suggesting that the benefits of using RISC OS are so tiny that they are outweighed by the 20 second delay, once or twice a day, as VRPC loads up. If that's the case then, frankly, no amount of cheap dedicated hardware (or whatever you are proposing) is going to keep people with RISC OS!