No. To my knowledge no mod author has figured out how to do that yet (keep reading though ).
I see from the research I did earlier today that you've been looking for a solution to this for ~2 years. I respect your tenacity. Never give up eh
I'm confident it's about to pay off This is more of a workaround than an overt solution but if you still need it for Machinima videos etc I think it will work perfectly for you. It goes like this:
Have a look through 'loadouts.meta' & make a note of all the guns the cops/enemies you plan to fight use.
For me it was these:
Depending on how you have the cops/swat etc armed there may be more so you'll have to hunt for them, possibly in other weapon meta files.
All those ones above are in the 'weapons.meta' here anyway:
Open up the file & set all of the cop/swat etc weapons damages to zero:<Damage value="0.000000" />
That's it. Done. No blood will show when those weapons are used to shoot someone.
The only real downsides to doing it like this are:
A )- The cops/swat/army/enemies etc can't kill the player when using those weapons.
B )- Your player can't use any of the guns the cops/swat use or if you do you won't be able to kill anyone with them & no blood will show when you shoot someone with them. Your enemies will ragdoll, but they won't die. All other weapons will work as normal (blood, death etc).
C )- When the cops are shooting your player he/she will twitch slightly when hit (looks kinda cool actually, very Terminator 2).
Possible Solution for A )- :
One possibility here (if you did want your player to eventually die) would be to leave 5 star dispatch peds with weapons that could kill the player. Could make for some epic Ned Kelly style last stand videos.
Possible Solution for B )- :
The cop etc weapons are not the most vital of weapons anyway (plenty alternatives) but if you did want to use them against the cops it would be easy enough to create new cop specific versions of them with zero damage in the meta files (COP_WEAPON_PISTOL etc) & then assign them to the cops in 'loadouts.meta', leaving you free to use the default versions for your player as normal.
Possible Solution for C )- :
I didn't test this but I'm sure reducing the '<Force value' to zero in the weapon's meta file will get rid of the twitch when the player is shot (or alternatively, raise it if you want more twitch):
Hope this works for what you want. Let me know how you get on (& I wanna see that video )