its not really going to be a popular idea with BBers as the whole point of running a course is to create that Anabolic environment thats necessary for growth. Even if you did get a good bit of size from this course, its only going to be natural that you'll lose some when coming straight off, even if good pct is followed. and throughout the year it will just be really tough to maintain what you've got yet alone build on it. thats why the constant cycling is needed, so you can always make gains on what you've got from the last one.
If you look at a lot of the older guys who've trained for longer, they have got a lot more mature muscle there as they have built up that muscle over time and their body has been in that highly anabolic/androgenic state for a prolonged period.
With powerlifting it may be a different case as you could use it just for a competition, such as taking halo or something but i would still think its gonna be the same.