1. One must have a program to be able to modify the assets*.pk3 Pkspace or Winzip
and much of free diskspace (about 1GB)

2.With winzip rename the assets*.pk3 -s from both of the games to assets*.zip -s

3. Find your map (for example ffa_deathstar.bsp)

4. Extract it.

5. Put it into assets1.zip of JA where other .bsp files are

6.Copy folders shaders; textures; ext_data (if you want rebornfencers etc.) ; music; sounds to assets0.zip of JA

7. Rename to *.pk3 -s (don't delete the files you copied yet, in case something went wrong)

8. Try it out. Start JA and bring down the console (shift and ~) type in devmap ffa_deathstar.

9. Enjoy...

Excellent! Thanks for the tip.

I don't know if you have tried this yet, but I suspect you do not need to alter the assets0 and 1 pk3 at all. You should be able to create another .pk3 with the same directory structure as the assets0 and 1 and it should work okay. I haven't tried it though, but that is how JO worked for the most part.

That's how all the Q3 engine games work I know of, no need to modify current pk3's, in fact it can cause problems on pure servers if you start modifying PK3's.