I'm using the Steam version of Morrowind in Crossover. Everything worked great except the texture replacements that I wanted to use. Changing the BSA attributes on the Mac turned out to be pretty simple, and it'll fix a lot of problems you may experience from addons.
Open up Terminal and use the following commands... For simplicity, I copied the three BSA files to my root folder and then put them back in afterward, but you could alternatively spell out the path to your bottle's Morrowind Data Files folder.
touch -mt 200205010000 /Morrowind.bsa
touch -t 200205010000 /Morrowind.bsa
touch -mt 200211060000 /Tribunal.bsa
touch -t 200211060000 /Tribunal.bsa
touch -mt 200306030000 /Bloodmoon.bsa
touch -t 200306030000 /Bloodmoon.bsa
That was enough to get things working for me! Enjoy your new textures! I recommend the Visual Pack here: http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=2915#Files