Recent work conducted under the aegis of the US Burning Plasma Organization related to establishing recommendations for requirements for ITER disruption mitigation systems is described. The recommendations and assessments of the resulting plasma and tokamak operations impacts of a massive-gasinjection disruption mitigation system have been developed in concert with the ITER Fusion Science and Technology Department. Several recommendations are made for the system: high reliability, large flexibility in the choice, mixture and quantity of gases, and its installation in at least two toroidal locations to provide redundancy. The large quantity of deuterium or helium neutral gas, ~500 kPa-m estimated to provide unequivocal collisional mitigation of runaway electron conversion is found to have significant after-injection impacts on the ITER torus vacuum pumping and exhaust processing systems. These impacts are reduced but not eliminated by employing neon injection. The impact assessments have highlighted needs to limit injected gas quantity to the minimum necessary for adequate runaway mitigation and to optimize the plasma uptake of injected gas or particles delivered to the torus. A variety of alternate or optimized gas, liquid and solid injection mitigation schemes and/or consideration of enhanced stochastic losses that may offer mitigation efficacy relative to presently-conceived basic, single MGI options have been identified.