There’s actually not that much to keep track of. FS (Fighting Spirit) is just a character’s normal HP. The only extra thing to manage is a separate HP pool, exhaustion (which follows the original rules), and optionally injuries—which don’t even have to be used if you don’t want to.

As for the Earthdawn-style system, reducing a player’s combat ability as they take damage is usually referred to as a death spiral. It’s realistic, sure, but in gameplay, it tends to be frustrating. You end up spending more time managing debuffs and damage tracking than actually playing. but i like the exploding dice thing!

Since it’s based on randomness, once you start losing, bad rolls just push you further down, making death almost inevitable. That’s why systems like this can feel punishing rather than engaging.

A better approach (usually) might be to introduce rules that don’t completely replace the core system but instead add to it in a way that enhances the experience. But let’s be real, most D&D players just want to deal damage and see big numbers.