While it may not run too well, it is possible to get Final Cut Studio 3 to install with less than the 'required' 128MB VRAM.
Control-click on the installer package alias and choose Show Original from the pop-up menu. Control-click the original installer and choose Show Package Contents from the pop-up menu. Navigate into the Contents » Resources folder. Control-click on the Requirements Checker and choose Show Package Contents from the pop-up menu. Navigate into the Contents » Resources folder, and then open minsys.plist with Property List Editor, the default (requires Xcode).
Change the value of AELMinimumVRAM from 128 to 64 (or less if you have even less VRAM). The installer will now run normally.
After installing, Control-click on the Final Cut Pro.app in /Applications and choose Show Package Contents from the pop-up menu. Navigate into Contents » Resources folder. Open the mimsys.plist file found there, and make the same change as above. Repeat for all the Final Cut Studio apps you have installed.
No promises on how well they run with less than 128 MB VRAM, but they do run.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090728144834364