I think the incipio battery mod looks fine, and i love the soft texture of it.
I think the thickness is fine, the weight though is too heavy. Despite this it's still handy to be able to stick it on the back if you need a few extra hours of battery life till you can reach a charger (without being tethered to a battery pack)
I agree on the idea of a smaller 1000mah battery mod. I'm getting used of how light the Moto Z is, but it almost feels too light, like I could easily drop it because there is no weight holding it in my hand. That could be just a placebo affect, I haven't dropped it yet!
Having a 1000mah battery pack might be that perfect balance of weight, not too heavy, not too light, whilst giving you a little extra juice. I'm actually finding without a battery mod I consistently get 4 hours SOT, which is decent battery life for me without a mod. So I wouldn't be phased at all if the mod only adds say 1 extra hour SOT. If the weight was good, I may keep it permanently on my phone. Even better make a 1000mah battery pack, which wraps around the sides of your phone as well, like a case.