Think I found a work around to use both APS System and PIR Reaction System

Use https://steamcommunity.com/sharedfiles/filedetails/?id=1974617455 (ACE3 with Various Medical and things that can effect other Medical systems removed)
and https://steamcommunity.com/sharedfiles/filedetails/?id=2537512642 (PIR (ACE Compat)

the PIR Ace Compat doesn't actually require ACE it just has it so PIR Reactions happen from being Hit (Essentially the Medical System is disabled by the Reactions remain)

The ACE I posted will work well with APS Medical system because it doesn't have the Medical systems that can affect it

AI will Revive you and teammates and Armor Protection does work

You ever get this working with new PIR?

I tried with these settings but here is what I got:

Just by changing these SIX settings from PiR's addon settings---
["Disable Standard IFAKs:"] OFF
["The possibility of instant death for Player:"] OFF
["The possibility of instant death for AI:"] OFF
["Number of Additionally IFAKs"] 0 (ZERO)
["List of replaceable IFAKs:"] *LEAVE IT EMPTY
["List of replaceable medkits:"] *LEAVE IT BLANK

This does the following:
- PiR will no longer replace the vanilla IFAKs and Medkits with it's own "PiR" versions- but AI can still PiR revive allies!
- Will not kill you instantly!!! (unlike PiR does by default)
- Any ALLIED AI can revive you!!! (if they make it in time before APS or PiR's death timer finishes...)
- Hit reactions play whenever you or AI get hit (and armor breaks accordingly)- instead of instantly dying!!!
- When you get hit and play a hit reaction animation from PiR- OPFOR AI will stop shooting you for a few seconds to let you catch your bearings.
*Feels very unintended but it's good for casual gameplay lol. To give you a breather.

Example images below of my testing. With diwako's hidden message.
https://imgur.com/a/2ndZaAr

BUT AI reviving you is a bit weird... and it seems since APS uses vanilla medkits to BOTH auto apply to player and AI when applicable (aka they are bleeding or took damage)- they are instantly used and you're back to incapacitated state I think too? It's weird. A lot of dead body inventories with no ifaks. I need to do more testing on this side.

Edited:

*USE THIS FOR SMOOTH PIR + APS

Using this mod with PiR(+PiRace) it GODAMN WORKS!
Just by changing these TWO settings from PiR's addon settings---
["The possibility of instant death for Player:"] OFF
["The possibility of instant death for AI:"] OFF

This does the following:
- PiR will replace the vanilla IFAKs and Medkits with it's own "PiR" versions- but AI will revive you and allies as per usual (before APS or PiR's death timer finishes...). You won't be able to self-revive though because there are no Vanilla IFAKs. Only PiR IFAKs. Which don't apply to APS self revive functionality.
- Will not kill you instantly by random!!! (unlike PiR does by default)
- Hit reactions play whenever you or AI get hit (and armor breaks accordingly)- instead of instantly dying!!!
- When you get hit and play a hit reaction animation from PiR- OPFOR AI will stop shooting you for a few seconds to let you catch your bearings. Good for casual gameplay lol.

Example images below of my testing. With diwako's hidden message.
https://imgur.com/a/2ndZaAr

END NOTE:

This all could use some fine tuning with the medkits and IFAK behavior but it's all working together nicely. Specifically with the two instant death options OFF.

See my new discussion for the full guide to get it working. Ignore the guide above. It's outdated.

https://steamcommunity.com/workshop/filedetails/discussion/2523439183/3814034217022099896/