I'm pretty sure ALMOST all plants can be bonsai'd. The biggest deal would be keeping it root bound.
I have a good friend who has bonsai'd tons of different species. You need to find a way to get it root bound (having the roots use up the space in the container). You would occasionally need to trim the roots back to give it more room to grow.
The only problem I see with attempting to bonsai hops, is that they build large root systems (if I understand correctly). I'm sure its possible, but it might be tricky. Good luck man!