Ply's Mod is the closest you're going to get.
It will let you:
1) Over-Ride the decal used for non-character hits (walls, entities)
2) Over-Ride the decal used for character hits
3) Prevent bulletholes from appearing
With a bit of scripting and setting up, you could even get it to use random decals when shooting. Just try the following:
- Make 3 weapons that are all the same in every way, EXCEPT for the decals they use whens hooting charcter and no-character objects.
- Make a script that will randomly "replaceweap" your weapon with one of the 3 you made. This change is INSTANT, meaning it won't interrupt anything if you have the weapon out already.
The only thing you're asking for that can't be done is having the decals stay there permanently. Decals don't naturally kill frame-rate but when you start building them up over time, it's going to catch up to you.
If I remember correctly, the maximum amount of decals FPSC normally allows at any one time is around 100... in Ply's Mod I upped that to 499. So, dynamically making decals and KEEPING them there... you're going to hit that cap very quickly.
The one and only,
Those who live in the past, are destined to insanity. Those who live only for the future, will be slaves to their ambitions.
Those who live in the moment... only they, are truly happy.