Im ok with that as long as you can keep it compatible with my release. Compatibility can be assured by following one of 2 sets of options described below.

If you want to use any assets in their current state, you can make hard copy of required files but make sure you correctly

• change file names of luas
  
• change att.names IN luas
  
  
• change file names(or paths) of copied models
  
• change material PATHS IN modified models(.mdl files)(includes editing vmts)
  
  
• change file names(or paths) of copied reticle materials
  
• change material paths in luas to match modified reticle material names
  
  
• change file names(or paths) of copied sounds
  
• change sound paths in luas to match modified sounds names
  
• change sound script/names in luas

Examples:

• HereTic's ECW Pack https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=375825081

Alternatively, if you dont want to waste your time in hex and text editors, you can enable my attachments only when my HK416 swep is present by checking state of global CustomizableWeaponry_KK_HK416. That way you ll use my release, no need to copy or edit any files, not even after I release update. Simple as that.

Examples:

• from my XM8:
  if CustomizableWeaponry_KK_HK416 then SWEP.Attachments = { /*attachment table containing HK416/FAS2/CoD4 attachments*/ } else SWEP.Attachments = { /*attachment table containing only XM8 attachments*/ } end
• other:
  SWEP.Attachments = { /*attachment table without my attachments*/ } if CustomizableWeaponry_KK_HK416 then table.insert( SWEP.Attachments[1].atts, 2, "md_fas2_aimpoint" ) table.insert( SWEP.Attachments[1].atts, 4, "md_fas2_leupold" ) table.insert( SWEP.Attachments[4].atts, 2, "md_hk416_bipod" ) ... end
• G4P UECW pack https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=359830105
  
• G4P UECW AWM EP https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=377460286
  
• CZ-805 BREN CW2.0 https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=395295283
  
• More examples in OP here.

If you have any questions related to this topic, ask below in Replies section.

Regarding backup sights and holosight:
I recommend using these attachments the #2nd way.
Their state should be considered stable-wip rather than finished.