Unchained/Inner Release vs. Inner Beast/Fell Cleave an Steel Cyclone/Decimate

[Reynhart]

but why can't they implement that for other jobs that basically share the same slot.

I think you're talking about "skills". Personally, I wouldn't make them "share the same slot"...I'd fuse them. Like Equilibirum, Inner Beast could behave differently depending on your stance, with its Deliverance version not healing you but adding 150 potency. And Steel Cyclone would not give enmity but also have a potency increase.

There's no reason for WAR to have less skills than other because of their stances.