not a big deal (with low price netbook).
you can use a android phone, too ... just for Bitcoin (only this installed, wifi ... no SIM card).
compromise PC is always because of multiple usage and multiples users ...
A PC is definetly a better choice for managing a cold storage. With an android phone, afaik, you can't sign offline transaction, so now there isn't a very secure and reliable way to administrate an offline wallet.
What's wrong with booting a USB stick? Is it just the possibility of a hardware keylogger?
Your USB stick could be infected with malware and keyloggers, and the computer you plug it in too, so there's no difference.
If you build the USB stick the same way you would build a computer, why would the USB stick be more dangerous?
Because it can pass malware onto any computer it gets plugged in to.
In order to install Linux on a separate offline computer, I would need to set up the install on a USB stick anyway. Doesn't anyone run cold storage on a bootable USB stick?