I was waiting for somebody more knowledgeable to comment.
AFAIK there is no current LV2 plugin equivalent to the HOG 2. What you can do currently is use several of the pitchshifters set to different octave intervals and mix the outputs. This doesn’t do any of the sequencing or fancy stuff but at least gets you the basic ability to add harmonics.
Maybe somebody will make a plugin with all the same features. I’d certainly like to play with such a thing. The rkr sequence plugin might get you close. http://rakarrack.sourceforge.net/effects.html#Sequence
Pitch shifting in general is a difficult DSP problem, usually a tradeoff between quality, CPU intensity, and latency.