Well, it must be a more than appealing system for you guys to withdraw what was previously done. All that defending of the current system, and all that tweaking of it to get it right to be able to do so... for weeks, if not months. I'm excited to see.
Well ISS is confusing to new players, most of the team didn't even understand it when they got to play A18. Why is my max health damaged? No clue. Then things like broken legs were fun and communicated well and created lots of interesting stories. So the idea was get rid of the confusing part, add more of the fun and interesting parts and it should be a nice system then.
We'll have stun which leads to concussions, cuts, deep lacerations (requires a first aid kit which has a sewing kit as part of the recipe) that causes periodic bleeding until treated, abrasions, broken legs, broken arms (slow reload, power attacks hurt the player 1hp, slower aim, etc) and a few other surprises. But the entire system is governed by a crit manager that decides if you get a crit or not. We'll have some protection in there for cheap crits too, so generally it will be like infection, if your armored up and high health you will be unlikely to get a crit (aside from broken legs). But the more beat up you get, and if you take a flurry of hits, then the likeliness of getting one goes up.
I'm really excited about it. It will communicate just like infection, with a debuff telling you exactly why your max health is damaged, and the amount with a number, and full description in the active effects.
Then for A20 we'll have the same setup for vehicle criticals, flat tires, punctured radiator, etc and specific parts to fix those problems.