Isn't one of the main points of Tor that other than by knowing that an IP is an exit node, no one is able to tell you're using it? And .onion resolution is entirely client side, no?
It's super difficult to build a low latency mix-net that covertly works inside an adversarial network.
In addition to the current models over which onion/garlic routing are based upon you would (at least) need to add to the core of your software traffic obfuscation, a series of covert channels, NAT bypass, ...
Tor and other mix networks simplify the problem assuming that there's a portion of the Internet that is free and introducing censorship circumvention mechanisms.
