The preflower area is 12/12. The only reason I call it that is because plants will only spend 3 weeks under it, preparing for the intensity of the 600 or 1000 watt.
Hey dude. If you have a separate veg/cloning area, then your plan will work just fine if you change the timing up a bit. Unless you are running 12 week strains.
With an 8 week strain you could rotate
2 weeks preflower under 400w
2 weeks flower under 600w
2 weeks flower under 1000w
2 weeks flower under 600w
With a 9 week strain you get pretty close alternating on the 15th and 30th/31st of the month, etc.