Unless he is climbing up the rope itself, i think the real value of the line is in the elasticity. Certainly in this application a measured amount of elasticity is mandatory, the length of the line the best place to get it. The rule of thumb i was brought up on was that a man falling 6' and caught by side D's will rip his spleen out; so lanyards were made to 6' and brought around a device, so you would only fall 3'.
Also, buying a higher tensile of line of the same materials and braid is not always wise, for as the SWL of the line goes up, the elasticity goes down. This gives more shock to the human cargo, or other load, and the support too. For the line links both support and load. The effect especially true on shorter distances of line used in system.
Exception being if that length of line serves another support leg to load (like climber's DdRT and rigger's DWT), then tensile is doubled; and at a static stand the support is loaded less. But on the dynamics of movement,the loss of elasticty comes into play (due to higher tensile of doubled line instead of single one to load of climber etc. on line); and the body and support are loaded more. More rope in system making up for some of the loss of elasticity, as long as it does not add more legs of support, increasing system tensile.
So elasticity is important, and with 200# men on 6000# rope doubled over to increase what line will hold; the elasticity is probably more important than the strength.
