FixedBufferAllocator is meant to minimally viable like in settings when there's no shared concept of "printing" or an OS for that matter. Check out LoggingAllocator which can take/wrap the former.
Maybe put the word "Sequential" in the name (like FixedBufferSequentialAllocator) to really hammer it down that you can't randomly delete. Then also have a movable head pointer so you can still deallocate in either reverse or forward order, it will still successfully free everything.