finders scriptability sux. You are not even able to change the icon of a file through applescript.
Icon formats and behaviours have changed lots since OS 9 and back, where Finder scripting was able to interchange them. Now we have bundles and icns, carbon apps with iclx resources, and some other files to store folder’s icons. I think these are great features for the system, though bad for scripting. Anyway, Finder’s scriptability doesn’t strictly “sux”. Only Finder icon scripting.