Controlling cadence was not an option on the C-17. USAF demanded that troop exit be safe independent of cadence. Another solution successfully used on the C-17 was a 10 ft static line extension. At first this resulted in a pissing contest between USAF and US Army. The Army owned the parachutes and wanted them to all be identical independent of the aircraft they were jumping out of, so they wanted USAF to own (and pay for) the extensions which were only required for the C-17. USAF refused. The solution was for everyone's parachute static lines to be permanently 10 ft longer, with USAF paying for the mod. I would think this solution would work for A400 also. But if that is the chosen solution, Airbus might be on the hook to pay for the extensions. These things get complicated and nasty pretty fast.