Hacker News Reader

There is not only one but actually two separate CS 1.6 recreation projects floating around. CS: Legacy and Classic Offensive

Check out "CS2D" - it's exactly what you're describing and has been running successfully for years with an active community and regular updates.

CS 1.5 has been clean room re-implemented GPL Quake engine, just need assets to make a fully free Counter-Strike.

https://github.com/eukara/freecs

The problem with mods is that there will be a million different mods with a million different rules A million different levels and behaviors, and you won't get good traction on any any specific style of gameplay, and people will not keep coming back.