Huh. I just had a go at setting this up myself, and I was quite happy to discover that this is much, much easier in newer versions of Fusion than it was last time I tried: It's basically "plug and play" now, with no need to modify any configuration files or anything like that.
If Fusion doesn't automatically offer to connect your Intuos 5 to the virtual machine, just look in the Virtual Machine menu, under USB & Bluetooth, choose your Wacom tablet there and Fusion will disconnect the tablet from the Mac and connect it directly to the virtual machine. Then you just need to ensure that you have the right Wacom driver installed in the guest OS, and you should get full support for all the tablet's functions within the virtual machine. You can also move the tablet back and forth between the VM and the Mac using the same USB & Bluetooth menu again.
Cheers,
--
Darius