OK...first of all, do you need this to have a quantizer for the incoming CV? Some harmony modules have this, others don't. If this is only ever going to see CV from MIDI or a keyboard or any other controller that outputs properly-quantized scalar CV, then you might not want this to have quantizing at the input. BUT...
...consider this: what if you want to use it without that controller's output? What if you want to take some voltage curves and then quantize these for chordal use? This could be quite useful. So unless you're absolutely, 100% sure that you won't ever use an input quantizer with this module, you might want that capability.
Second, you want memory. Something like this works much better if you have a way to store progressions and/or parameters for harmonic extrapolation. If I were you, I'd only be looking at modules of this type if they provide a storage method.
Third, you really should have a plan for using whatever you put into a modular system, particularly if the device in question costs a chunk and occupies a lot of panel space. Sure, these look like they solve a lot of issues. But then again, so would a laptop, the right software + an Expert Sleepers interface with an expander or two. Furthermore, you can use that ES interface for a zillion things, wheras a harmony module is great as...well, a harmony module. Can it record what you do on the modular? No, but the right ES interface can. Can it host a USB controller? Probably not, but the right ES interface can. Can it...well, you get the idea. Building a successful modular synth requires plans. Figure out what you want to achieve sonically FIRST...then start figuring out optimal ways of accomplishing this. Unless you have loads of space planned for your build, chucking in a one-trick module such as a chord generator may well be the exact wrong way to do what you're trying to accomplish here. Step back a bit until the G.A.S. rush dies off, THEN start trying to figure out how a system like this would fit into what you do. Do you even have a clear picture of what you want to accomplish musically? If not, then you might wind up building a very expensive thing that sucks in $$$ and only outputs annoyance.