How much, if any, would this double run and combiner scenario help?
If you only have 16AWG cable available, rather than trying to parallel and combine them, just split your equipment so half of it is connected to the first cord and the other half is connected to the second cord. Much, much safer.
If you're using a power sequencer, you'll have to manually sequence your equipment.
The scenario of having only 16AWG cable to run that distance is a symptom of poor planning. If, for example, this was a wedding and you DID advance the show with an onsite visit, and by the day of the event the coordinator decided to have the ceremony in a different location without informing you, and suddenly you need more extension cords and the only ones available are the orange cords they scrounged from the barn, that is THEIR problem, not YOURS.
"But the show must go on!" Not at the expense of safety. Either you move to a location closer to power, you reduce your load to meet the capacity of the cabling, or you delay the event until you can get proper power.