Antzy:
The thing is Atmega8 is easily available...
How many do you need? DigiKey has more than 10,000 ATmega8U2 processors ready to ship. Seems "easily available" to me.
...and more popular.
Prove it.
Can't we emulate the USB hardware in atmega8u2 in software, like used by USBtinyISP to connect to PC via USB?