Is there a way to fix the collisions in swbf2 objects when using them in swbf1? (without using xsi) I used the geonosis bunker platform in my map from swbf2 and ingame it had no collision at all!

if there is a .msh.option file with -nocollision in it remove the .option file

And that will remove the collision?I will try this since i have the same problem with the Utapau models. (invisible walls,roofs...etc)

The only way (without xsi) is to place invisible models against the walls and floors.

You can hex-edit the objects and rename collision objects (Usually something like "P_-so_cube101" to "collision101"), the same way you can rename mesh objects within a .msh file (after the NAME section)