Aircraft oils is nice, for their intended purpose...
They are made to function in very cold conditions, means they are thin.(its very cold up there)
Some of them then don't work very vell in normal and hotter temps.(because they are so thin)
Some are in fact based on water...to be flame resistant.
And then some of them has some nasty aditives to have those special caracteristics.
H-544 is a type used in military equipment, and it causes cancer if you inhale gasses from it....
Its cheaper and easier to do your regular maintenance, and clean up the engine room, instead of designing your equipment for those oils...
We talk about new pumps, filters, bigger cooler, special valves, special o-rings, special hoses, special everything...
Most main battle tanks use electric systems instead of hydraulics.(turret and gun controlls)