Chris
What I said was that if the engine failure were accompanied by loss of fluid in one of the two systems that power the brakes, I would have 50% of brakes. The brakes on Challenger/Global are divided inboard and outboard powered by system 3 and 2, respectively. Yes, it is a compounding emergency, but loss of fluid quantity could be caused by uncontained hot bits from an engine disintegration. The brakes normally have two pumps powering them-AC and Engine-driven, so it is a remote possibility. Once the fluid is gone, no power for those systems. The C-5 was similar where loss of system fluid required switching to alternate brakes-just a switch actuation by the Co-pilot, but easily missed in the heat of a overspeed abort. But you did then have all the brakes.
My point was it is better to address these issues airborne. I presently have plenty of brakes for stopping with a 50% loss, if it is planned for.
BTW, the C-5 has a low Vmcg of around 80 knots, dry, no crosswind. We computed corrections for both runway condition and crosswind. I'd like to think the low Vmcg was due to having four very powerful APUs as engines.