Re: O2 many issues
Remember that the reason the Harrier does short take off and vertical landing on the old British carriers is operational. With a full combat load, the Harrier doesn't have the power for a vertical take-off. Landing on the other hand you have minimal fuel, and have likely dispensed with munitions as well, so vertical landing becomes feasible.
Water available for the water injection minimises time in the vertical, but realistically, time in vertical for take off and landing is minimal anyway.