Why you cant add the Shift, Force, or Decay stuff into HL2.

While you can import the HL:s assets into HL2, some won't work, or fit the vibe of the current area. And there is no models for:

• Alyx
  
• Metrocops
  
• Breen
  
• every citizen and rebel
  
• Some weapons, like the AR2

And yes, while you can replace the combine models with the hgrunts, lorewise, it doesn't make sense.

In Opposing Force, Blue Shift, and Decay, they all run in GoldSrc, a engine different from Half-Life 2's Source.
Since GoldSrc uses a different BSP and the WAD3 file, the predecessor of WAD2, a file made by id Software for Quake, containing textures, you would have to convert it to a format readable for Source, which is tiring since i did it before, but that DOESN'T mean im going to do it for this.

You would have to convert every BMP file in Half Life to a VTF, and I'm not sure how you would do that, since I don't map for Source that much.
If you could import every single model into, wait, hold on, I'm gonna check if they use the same file structure... oh, they don't, well, I'm too lazy to explain why, so I'm gonna let Gemini take this over.

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While Source was built from the GoldSrc engine code, the model formats have significant differences and are not directly compatible. Here are some reasons as to why the don't work. In GoldSrc, textures (BMP format) were compiled directly into the .mdl file or stored in WAD files. In the Source engine, textures are separate files in the Valve Texture Format (.vtf), which are referenced by a material file (.vmt). The .mdl file itself only references these materials. A GoldSrc model typically consists of just the .mdl file (and sometimes separate files for animations like modelt.mdl or zombie01.mdl, which were specific parts of a single model's structure in an archaic format). A Source model, however, is a collection of files that must all be present to function correctly: .mdl, .vvd (vertex data), .vtx (or .dx80.vtx, .dx90.vtx, etc., hardware-specific mesh data), and sometimes .phy (physics data) files. GoldSrc .mdl files are all version 10 (for retail games), while Source engine models generally use versions greater than 25, often starting with version 14 in early betas, and use different internal identifiers. The two engines use different compilation tools and processes. Porting content between the two requires specific conversion tools and steps, as the file formats are fundamentally different in their implementation and accompanying data.

Due to these differences, you cannot simply drop a GoldSrc .mdl file into a Source game's directory and expect it to work, nor vice versa. They must be converted using specific porting guides on the Valve Developer Community wiki.

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Thanks Gemini. Anyways, keep reading this please.

If you could be able to, it would probably take a couple weeks, or 5 days if you're lucky.

I hope whoever posted about it understands the struggles of doing it, and checks out my COOL WORKSHOP ADDONS FOR HALF-LIFE LEGACY!!1!
https://steamcommunity.com/sharedfiles/filedetails/?id=3644184693
https://steamcommunity.com/sharedfiles/filedetails/?id=3644942799