The issue with usb switches is u need one that cuts the power when you switch inputs, this allows the wheel to reset. My guess is that most do this but, I didnt feel like spending $15 on a switch that would not work so I went the old school way and used usb extension cable and I just lift my CP and plug my wheel into whatever I want. It takes 5 seconds but, that may not be an option for you if you Control panel does lift up easily.
The PS3 would need to be jailbroken to play without disc. I had my done by someone on craiglist for $50. Once jailbroken, you can rip your own real games onto the HDD. Game vary in size but to give you an idea how much hdd space you need, GT6 is about 20gb (one of the largest racing games) but most racing games like NFS hot pursuit, shift 2, midnight club, etc are about 6-7gb. The ps3 can be turned on by pressing the ps button your wireless controller, you can keep the ps3 hidden and just keep a wireless controller around. you can turn it off with the ps button too.
doubling the buttons is easy if you know how to solder and hard if you dont, just take wheel apart find the button circuit board and wire in new buttons. There are plenty of videos on youtube of people wiring the "O" button to a handbrake switch.