The problem is that outside the SI system you would not necessarily use the same base and derived units if you want to stick to standard speak. Torque in pound-feet, revolutions in RPM. Try to make that into horsepower... The beauty of SI is its consistency: five or so base units, and everything else is 1:1 derived from these units.
But I don't need to tell you this, I guess... :-)
"Air Force bla, descend 3.000 feet, QNH 1013" "Can we have that in inches please, sir?" "Sure, descend 36.000 inches, QNH 1013"