Re: RNG as an Internet service?
"It would be pretty trivial to use a bank of hardware RNGs to feed a server that will supply a different random number each time one is requested."
...which instantly makes hardware RNGs pointless in this context. The whole point of a network like TOR is that there's no 'home', no central hub that can be used as a point of attack.
Either you have to have a central set of hardware RNGs feeding the TOR network (that the authorities could take control of) or each TOR user has to buy a hardware RNG generator to use the network (that authorities could attack at the manufacturer level - and considering they would probably end up being manufacturer in China...).